Once upon a time, in a house by the side of a canyon at 8776 Lookout Mountain Avenue, there lived an obscure (to most of the world) young author who jokingly called himself the Hermit of Hollywood.
On the wall of his study, there hung a chart—"an outlined and graphed history of the future with characters, dates of major discoveries, et cetera plotted in."  Nothing like it had been seen before.
The author, of course, was Robert A. Heinlein and the chart—or, at least, a later version of it—can be seen in the opening pages of any book in his "future history" series—THE MAN WHO SOLD THE MOON, THE GREEN HILLS OF EARTH, REVOLT IN 2100 and METHUSELAH'S CHILDREN.
Heinlein's chart came into being around 1940—a year that now seems remote, both to the world at large and the world of science fiction. Atomic energy, space travel, and "future shock" were unheard of, except in science fiction—and science fiction itself was virtually unheard of.
These were the days when John W. Campbell Jr. was first struggling to make a "pulp" fiction into something respectable, and when the authors were still struggling to keep writing through such expedients as the Manana Literary Society (Anthony Boucher captures the spirit of the time, and some of its leading personalities, in his 1942 mystery novel, ROCKET TO THE MORGUE).
The pay was bad, but Heinlein and the rest had a lot of fun. And while they were at it, they made science fiction into a serious form of speculative literature.
Not that they would ever let on—except among themselves—but after Hiroshima and the V-2, they found themselves having to make fewer and fewer excuses for their peculiar profession.
Heinlein's "future history" stories and novels are now rated among the "classics" of what was once called the Golden Age of ASTOUNDING, the magazine where most of them originally appeared. The world has gone on to other things, and so has Heinlein. Or has he?
STORIES TO BE TOLD
Careful reading of the left hand column in his chart will disclose titles of several "stories to be told"—in parentheses. None of them had been written by the early 1950's, when Heinlein assembled his shorter-than-novel length fiction between hard covers, nor even in 1958, when the book version of his 1941 serial, METHUSELAH'S CHILDREN, was finally published.
Heinlein felt it necessary to explain why some of them—"The Sound of His Wings," "Eclipse" and "The Stone Pillow"—hadn't been written, and what they would have been about, in an endpaper to REVOLT IN 2100. But there remained an enigmatic reference, at the very bottom of the chart, to something called DA CAPO.
DA CAPO has now been written. Only the new title is TIME ENOUGH FOR LOVE, and the concept of the novel has (apparently) been elaborated far beyond what Heinlein first intended, more than 30 years ago, when he was still the Hermit of Hollywood. It is scheduled for publication this month (May) by G.P. Putnam's Sons. It may be a masterpiece, a disaster, or something in between-but it will be important.
Heinlein is emotionally a Middle American, intellectually a free thinker. This has always been both the strength and weakness of his work. At its best, his fiction combines a human warmth and intimacy unmatched nearly anywhere else in the genre with a highly imaginative, yet realistic, exploration of the possibilities of the future. At its worst, it can degenerate into mere folksiness, or the emotional and intellectual commitments can clash jarringly.
The worst was painfully evident in his last novel, I WILL FEAR NO EVIL, where his intellectual commitment to the idea of sexual liberation ran up against his ingrained Middle American values to produce a work that lacked either intellectual or emotional vigor. The fact that Heinlein was seriously ill when he wrote it didn't help any.
When Heinlein began writing, sex wasn't a big issue in science fiction—little attention was given it, at least in the explicit sense. Much has been said of the "puritanism" of the pulps—although the instant acceptance of Philip Jose Farmer's "The Lovers" in 1952 may indicate that the reader puritanism so long feared by editors was a paper tiger.
Even then, some of Heinlein's Middle American crotchets—such as a longing for personal immortality (see BEYOND THIS HORIZON) marred his work. But the "future history" series (he didn't call it that; Campbell applied the name) was free of such obsessions, at least in the narrow sense, and was pioneering both in its concept and in its execution.
As far back as H.G. Wells, there had been stories set in a single future society WHEN THE SLEEPER WAKES, "A Story of the Days to Come," "A Dream of Armageddon"). Olaf Stapledon, in 1931, created a vast—but impersonal—panorama of the possible future of mankind in LAST AND FIRST MEN. (Wells followed in 1933 with a dreary, short-range pseudo-sociological history called THE SHAPE OF THINGS TO COME.)
SERIES OF STORIES
But Heinlein was the first to create a series of stories, set in different times, with different characters, but all part of a common future that grows with each story. The technique has been widely adopted since by future historians as mythological as Cordwainer Smith, or as fanciful as Larry Niven.
Heinlein's major stories in the series were not merely consecutive, but functionally related. Events, technological innovations, sociological trends in one story influenced those in later ones. Always concerned with educating the public about the impact of the future (as witness his later "juvenile" novels, which really rank among his more mature works), he seems to have had an idea in the back of his mind about history as an educational process.
Early stories in the series—"The Roads Must Roll," "Blowups Happen," "The Man Who Sold The Moon"—fall into what Heinlein called the Crazy Years, a "period of semantic disorientation and mass hysteria"  brought about by the rapid pace of change. Thirty years before Alvin Toffler's FUTURE SHOCK, Heinlein was projecting, in the serial version of METHUSELAH'S CHILDREN, such 1959 headlines as "California Raises Voting Age to 41—Rioting on Berkeley Campus." 
It was this mass insecurity in face of revolutionary technological change that Heinlein saw as leading to the rise late in the century of Rev. Nehemiah Scudder, the television evangelist of the never-written "The Sound of His Wings" who established the theocratic dictatorship overthrown later in "If This Goes On.…" The "false dawn" of space travel, abandoned during the theocracy, was suggested in "Logic of Empire," and would have been dealt with more explicitly in "Eclipse."
Heinlein was influenced at the time by Alfred Korzybski's General Semantics, and the possibility of applying it to a science of "social psychodynamics" was explored in both "If This Goes On.…" and METHUSELAH'S CHILDREN. Scudder's theocracy used social psychodynamics to control the populace (as in George Orwell's 1984, published later). The framers of the Covenant meant to apply it more creatively, to prevent the mass psychological upsets and insecurities that led to Scudder's rise.
That Heinlein's interest in libertarian societies dates back much further than THE MOON IS A HARSH MISTRESS is shown in "Coventry," where, under the principles of General Semantics, the only crime is committing provable "damage" to another and criminals have the choice of exile or treatment at a "psychodynamic" clinic to have their violent tendencies cured.
In METHUSELAH'S CHILDREN, we learn that "custom" is the basis of individual freedom. Public places are under constant surveillance by police, and citizens are registered—all for purposes of crime control. Yet freedom is respected by custom, simply because the populace has accepted the idea psychologically. At first, this may seem absurd—but what ever enforced the freedoms of the British constitution but custom? And how much does mass psychological insecurity—rather than conspiracy—contribute to the contemporary rise of statism?
Heinlein realized that for a libertarian society to work, men had to become civilized—to overcome the tribal and barbarian passions of the past that created a ready social climate for intolerance, persecution and totalitarianism. In METHUSELAH'S CHILDREN, man wasn't civilized enough yet—the knowledge of the existence of "long lifers" produced yet another outburst of jealousy and mass hysteria.
The flight of the "long lifers" in a stolen starship, their encounter with alien intelligences more advanced than our own, and their eventual return to an Earth ready to accept them because it has "discovered" the "secret" of longevity they never had, form the background for DA CAPO, which was to have described "Civil disorder, followed by the end of human adolescence and beginning of first mature culture." 
For years, Heinlein kept 100 pages of notes for DA CAPO, which in 1967 he hinted was to deal with the "further adventures of Lazarus Long" (a key figure in Methuselah's Children) and "tie up the loose ends" in the "future history" series.  But the notes lay idle on his desk until—it must have been just after he wrote I WILL FEAR NO EVIL—he finally decided to use them in a novel.
But TIME ENOUGH FOR LOVE, obviously, is a far different novel than DA CAPO would have been in the 1940's. George Ernsberger, editor at Berkley Books (Putnam's paperback line) has read it, and while he doesn't know the "future history" series in enough detail to judge how well TIME ENOUGH FOR LOVE fits into it, he does have some startling revelations. 
The vast (250,000 words) work covers 26 centuries in the life of Lazarus Long, as recounted in his memoirs—ranging from visits to far planets to a time-travel trip to his childhood home, where he falls in love with his mother (the sexual liberation element is similar to that in I WILL FEAR NO EVIL, but "not as obsessive," according to Ernsberger).
Less argumentative than most of Heinlein's recent work, Ernsberger says, the novel is concerned more with the nature and destiny of man than with politics and economics as such—although there is a background that involves the spread of humanity across the galaxy and the establishment of independent sub-cultures of many planets to suit different tastes. There is "little commerce" among the planets, much less a common government.
Genetics seems to be a "controlling consideration," according to Ernsberger—incestuous marriages are all right as long as they don't produce defective offspring, while Heinlein (or at least Long) is all for elimination of the "economically incompetent" for eugenic reasons. The reliance on "custom and tradition" in ordering society seems to be carried on from METHUSELAH'S CHILDREN.
A "huge and energetic book," TIME ENOUGH FOR LOVE is less a novel than a series of interlinked stories—some as adventurous as the early Heinlein works. "This book has the feeling of a valedictory," Ernsberger says. "He broke out of traditional structure as if he wanted to get every last thing into it, whether it fit or not."
Yet Ernsberger considers it a far better book than I WILL FEAR NO EVIL. Heinlein seems to have worked out the problems that obsessed him in that book, he believes—now they can be part of the natural background of TIME ENOUGH FOR LOVE.
Well, the rest of us will see for ourselves soon enough. As the culmination of a series none of us ever expected to see completed, it is all the more important to us that Heinlein's new novel succeed. So let's keep our fingers crossed—after all, it was after the dismal failures of PODKAYNE OF MARS and FARNHAM'S FREEHOLD that he produced THE MOON IS A HARSH MISTRESS.
NOTES AND REFERENCES
 John W. Campbell, editorial ASTOUNDING, February 1941.
 "Methuselah's Children" in ASTOUNDING, July 1941.
 Lower right in "future history" chart.
 Personal conversation, 1967.
 Personal conversation, 19 January 1972.