I guess I look for in a good book is the author's ability to really develop the characters. Also when the author takes a character that would originally be looked at in the traditional evil light, and changes the reader's feelings towards that character. To be honest there aren't a ton of books that I have deemed a "good" book. My favorite is Dr. Jekyll and Mr. Hyde, and it doesn't exactly fit my good book criteria, but I love that book. I can't really point out what makes it good to me but it just is. When we read it last year in class, a lot of people hated it, but I thought it was wonderful. I still don't understand the book completely, because of the way it's written, and maybe when I figure it out I won't like it anymore.
I still can't say exactly what makes a book good. There defiantly is stuff that makes a book crappy, but it's like that quote "the beauty is in the eye of the beholder". I don't know if that's right but it sounds good. I think that a good book is when the author is able to really bring you into the book, mess with your feelings and have the book come to life.