Some good book covers according to me are:

• Fuzzy Dice by Paul Di Filippo
• Shades of Grey by Jasper Fforde
• any "Clementine" book by Sara Pennypacker
• 100 Cupboards by N.D. Wilson
• Peeled by Joan Bauer
• both "Mysterious Benedict Society" books by Trenton Lee Stewart
• most things by Haruki Murakami
• Deceptive Desiresby Serita Stevens ... just kidding. (Am I?)
• .... and of course ALL HARRY POTTER BOOKS EVER.