This is (probably) a great book, but it does have one significant barrier for the reader. I don't consider bringing it up to be a spoiler, since it's an idea and not a plot point, but if you hate even minor spoilage, you should stop reading NOW.

Time Enough for Love consists of a framing story, set in (our) far future, about the oldest man in the universe, and his reminiscences. The final section merges the two. It's less a solid, streamlined novel than a fixup. Which is fine with me; fixups are my favorite strategy for long-form fiction. The reminiscences (and the last section) are extremely readable, and I (mostly) found them hard to put down. The parts of the book that aren't centered on the main character are often tedious, cringeworthy, or both. (For instance, the leadup to the last section took me many days to get through; by contrast, the last section, which was perhaps 3x as long, was hard for me to put down.) The most famous of the reminiscences is the centerpiece, titled "The Tale of the Adopted Daughter"; it's often referred to among Heinlein fans as "The Dora Story", and Virginia Heinlein wrote that when Robert died, she turned to it for consolation.

The main character would be horrifically unlikeable in real life but, due to Heinlein's considerable skills, comes off as a charming, eccentric old coot rather than one of the hectoring lecturers who inhabit far too many of Heinlein's novels. (Of course, your mileage may vary.) One of the things I like is that he is clearly an unreliable narrator; he claims that some of the stories aren't about him, but about one of his friends, and the stories are larded with inconsistencies with each other and with the real world. (Or "our timeline", anyway.)

Why do I say this is "probably" a great book, and what is the significant barrier? This is a book about incest. Heinlein leads up to it gradually, and in a gingerly fashion, but it becomes more and more central to the story. (If there is a form of heterosexual incest that isn't featured here, I missed it.) I borrowed a copy of this book from a friend who's a bigger Heinlein fan than I am, and he warned me that it was a book he hadn't been able to finish (and he didn't want me complaining later that I hadn't warned him ;-). If it hadn't been for that warning, I might not have been able to finish the book (motivated slightly, perhaps, by my desire to finish a Heinlein book that he hadn't ;-). I therefore extend the same warning to anyone reading this.

(Finished 2010-09-15 0:08:59.6 +/- 0.01s, approximately.)