So many awesome suggestions.
For myself, I'd recommend (EXTREMELY short list, believe it or not.):
Sci-Fi: Anything by Robert Heinlein, but especially Stranger in a Strange Land.
Fantasy: David Eddings, Piers Anthony's Xanth series, Robert Jordan. And if you can find it, Ariel by Stephen R. Boyett.
Horror: Dean Koontz, early Stephen King.
Humor: Douglas Adams, Robin Asprin's Myth series. (If you like Star Trek, the series novels written by Peter David are hilarious.)
Classics: Anything by Jack London , Richard Adams' Watership Down, Lloyd Alexander's Prydain Chronicles, C. S. Lewis' Chronicles of Narnia.
Detective: Robert B. Parker's Spenser series.
As for a book club: Hell yeah! Being an amateur author myself, I'll happily discuss books, writers and writing all day long.