Here is what I use with a brief description. Bold items are ones that I have read this year so far.
Spoiler:
Adventure - The journey is the important part (Allen Quatermain, etc)
Children's - Kids books (Holes, Bridge to Terabithia)
Classic - Verne, Twain, etc. Can almost certainly be another genre too.
Fantasy - Swords and sorcery (set in a fantasy setting)
Fiction Misc - Literary or other non-genre fiction
Historical Fiction - Robin Hood, Civil War, etc.
Horror - More than just vampires
Mystery - Holmes, Marple, Drew, Hardy (not thrillers)
N-F (Non-Fiction)/Biographies - (Auto) Biographies, True Stories, etc.
N-F/History - History Books
N-F/Humor - Humor
N-F/Other - General Knowledge
N-F/Philosophy - Plato, etc.
N-F/Reference - Textbooks, manuals, etc.
N-F/Religion - Christian study or reference
Paranormal - Superheroes, mutants, modern magic, etc. (inludes urban fantasy like Dresden)
Post-Apocalyptic - Includes Dystopian (Hunger Games, Wool, etc.)
Religious Fiction - Lehay, Jenkins, Peretti, etc. (Left Behind, etc)
Science Fiction - General science fiction, i.e., medical, computers, etc.
Space SciFi - Aliens, space opera, military sci fi, etc.
Steampunk - w/ or w/o magic
Suspense - Less action, more suspense
Thriller, Legal - Crime, police, etc. (Grisham, Patterson)
Thriller, MedTech - Medical/techno thrillers (Crichton, Preston)
Thriller, Political - Military, espionage, conspiracy, etc. (Clancy, Ludlum)
Unknown - Books in progress by authors I follow that don't have enough description to classify yet.
Western - Lamour, etc.