This is a science fiction what-if; and worse, a fannish one. You have been warned.
1964: Earl Kemp, a science fiction fan, decides that there is a hole in the (then very small) literature of SF criticism: there is no book critically assessing the works of Robert A. Heinlein.
This would be no big deal, except that Earl is no ordinary fan. He's the head of one of the country's largest fan groups. And he's editor of Advent Press a small, semi-professional publishing house.
Earl drafts another fan, a college kid named Alexei Panshin. Panshin has few obvious qualifications beyond energy, intelligence, and one article on Heinlein in a fanzine. But what the hell: this was fandom, back in the day. Panshin immediately starts writing while running around trying to collect background material. (1)
1965: It all goes to hell.
Heinlein gets wind of Panshin's efforts and is first nonplussed, then annoyed, then /grossly/ offended. If you're a fan, you probably already know this story. If not, never mind... I'll give links below. Trying to be neutral here, we can say that Panshin was puppyish and clumsy, while Heinlein was proud and prickly.
Final outcome: Heinlein writes Earl Kemp (and many other people) a ferocious letter. It blasts Kemp and Panshin, forbids them to quote from his books or use his name or image, and threatens litigation.
Kemp backs off and cancels the book. He would later apologize to Panshin, and say that he regretted not standing up to Heinlein: "What I should have done was take Heinlein on; told him to get ****ed, and brought on the lawyers." But it's not easy for a fan, however prominent, to face down the world's most successful SF writer in his full wrath. So Kemp caves. (2)
Panshin is left with a half-finished book. He is at first crushed, but eventually decides that he will finish the book anyway.
1966-7: Panshin publishes pieces of the book in fanzines. By this time the story of Heinlein's smackdown is common currency (he cc'd half a dozen people), so the individual chapters are greeted with intense buzz and attention. In 1967, they win Panshin the first Hugo for Best Fan Writer.
1968: Advent (now run by Kemp's friend George Price) changes its mind and accepts the book. It's longer, more detailed, and -- in Panshin's opinion then and since -- better than the first version from 1964-5.
_Heinlein in Dimension_ is a nine-days wonder in fandom, and will go on to have legs; it has remained in print ever since, and is still a good starting point for furious arguments between and among Heinlein fans and SF readers generally.
And Heinlein? He never followed up on his threats. He did own a copy of _Heinlein in Dimension_, but it's unclear if he ever read it. (There's an arcane debate about this, as it's possible to point to some passages in his later works as responding to Panshin. We'll never know.)
So: WI Heinlein /had/ sued?
OTL Heinlein wasn't particularly litigious; he threatened suit on more than one occasion, but AFAIK only followed through once. In 1958 he sued a studio was about to produce a really bad B-movie ("The Brain Eaters") quite obviously based on _The Puppet Masters_. He ended up with a cash settlement, and the movie was heavily edited to make the copying less blatant.
That was the only time OTL... but Heinlein seems to have been sincerely furious at Panshin, who he viewed as a little troll sniffing away at his privacy. And Heinlein did love his privacy.
So let's say he truly loses his temper and sues Advent. To make it more interesting, let's say he sues in late '67, after Panshin has won his Hugo but before the book is published. He'll be asking for what lawyers call "injunctive relief" -- a prohibition that the book be published, because it will contain material that is libelous, scurrilous, or unlawfully obtained.
This is wildly unlikely to succeed, but angry elder statesmen have done sillier things.
What now?
Well, publication of the book is delayed, probably by a year or so. The lawsuit is eventually dismissed. By this time, Advent had incorporated (it was originally a partnership, but Heinlein's first threat of litigation made the owners decide to go formal) and had developed a sub rosa relationship with Hugh Hefner and Playboy (long story). So, they would have had access to deep pockets if need be, and would probably have been able to defend themselves, and eventually prevail.
_Heinlein in Dimension_ becomes a huge success, relatively -- it can actually be found in real bookstores, as opposed to being ordered from Advent. This is nice for Alexei Panshin, but otherwise there's probably no long-term effect.
More interesting is the question, what happens to Heinlein? Losing a court battle is always embarrassing, and more than one artist has been sharply affected by it. And Heinlein was not a man who lacked pride.
I could see this going a variety of ways. He might retire from writing for a while. He did this a couple of times OTL, though it never lasted. Say he sulks in his tent for... oh, two or three years. Given the timing, we might nor might not get _I Will Fear No Evil_, but _Time Enough For Love_ is probably knocked out.
Losing a couple of Heinlein's later works would have some impact on the field, but I'm not sure how much. This gets into the very fraught question of whether Late Heinlein was worse than Early and Middle Heinlein, and if so, how and by how much. Putting this aside, I think it's clear those later works had less /influence/ than his earlier stuff.
On the other hand, Heinlein was nothing if not tough-minded. So he might have just kept rolling on. I do think there'd be some impact on his writing, but it would probably be subtle. We wouldn't see dastardly young critics and treacherous publishers appearing as characters in his books; rather, I suspect we'd see a shift of emphasis. But I hesitate to speculate just how.
There'd also be strange knock-on effects on fandom, but I'm not fan enough to work that line.
Thoughts?
Doug M.
(1) Here's Panshin's version of events (longish, but quite readable):
http://www.panshin.com/critics/StoryHiD/HiDcontents.html
(2) Earl Kemp's version:
http://www.panshin.com/critics/Happens/happens.html
(This rambles, -- Panshin calls it "an undigested blurt of memory", and he's right -- but it includes a deeply weird account of Kemp's meeting with elderly, moribund multibillionaire Howard Hunt. Apparently Hunt had a science fiction novel in him. Just not a very good one.)
And the book itself:
http://www.panshin.com/critics/Dimension/hdcontents.html