Pretty much all of fantasy is a roman-fleuve as authors are expected to continue writing sequels if the first book proves to be successful: Earthsea, Game of Thrones, Harry Potter, etc.
But in terms of realist depictions of human life, I love the abovementioned quartet by A.S. Byatt written over the course of 25 years: you can see the characters change, but you can also see Byatt herself change, as a thinker, as a writer, as a stylist: all four books are so different in execution!
I know Patrick meant this thread to revolve around books alone, but I would like to mention three cinematic achievements that I think are peerless (because, again, you can see the actors change, and grow, and mature, and become different human beings, just like their characters!):
- the
Bill Douglas Trilogy (My Childhood, My Ain Folk, My Way Home)
- Truffaut's
Adventures of Antoine Doinel (1959-1979)
- Richard Linklater's the "
Before" trilogy: Before Sunrise, Before Sunset, Before Midnight (1995-2013)
Astonishing achievements, all of them!