What I usually like:
Entertaining, funny, dramatic, romantic, adventurous, young adult, humourous sci-fi, clever, inspirational but not cheesy, female empowerment, female protagonists.
Think Jane Austen, Wicked, Terry Pratchett, Douglas Adams, Diane Wright, Wayside School series, Catherine Called Birdy, Kite Runner, Rob Thomas (Rats Saw God), Poisonwood Bible, Harry Potter, The Count of Monte Cristo, Judy Blume, Sisterhood of the Traveling Pants, Nick Hornby, The Perks of Being a Wallflower, etc.
Not big on:
History, politics, corny fantasy (Daughters of the Moon), trivial high school experiences (Sweet Valley High/University), thrillers.