BookieLookie

You can:

• See at a glance whether a book is humorous, violent, sad or romantic.
• Set up your own sets of terms. For example, "funny" set can include "funny, laugh*, humor*".
• Wildcard support. For example, "humor*" matches both "humor" and "humorous".
• Sort books by title, year, author, reviews, average rating or your defined term sets.
• Limit results by # of reviews or average rating.
• Choose from popular lists or add your own.
• Click on book title to open the book page in a mini-window.
• Mark books as "read" and hide them.

Note: I'm not a certified Apple developer, so on a Mac you'll need to go to System Preferences > Security > General, and click "Open Anyway".