What do you Look for in a Book?

Since my readers on Mibba have helped me improve my writing immensely though their wonderful comments, I want you guys to help me help my friend. I am currently helping to "edit" my friend's book. When I say "edit", I mean comment here and there without rewriting everything. I'm really struggling with that at the moment...

Anyways, to the important question though: What do you, as a reader, look for when it comes to a good book?. I'm not asking for very specific details such as the color of the main character's hair or how tall a character is; I'm talking about in general. What makes a book a good book? Is it important that you can relate to the characters? Is it a good thing if you can feel what a character is feeling? Do you enjoy a book which builds up suspense and mystery, or one which you know exactly what's going to happen? Things along these lines are what I'm looking for.

If you could comment and tell me what you think, it would be AWESOME!! I really want to help my friend make this book the best that it can be.

Love,
Gaojou.

PS. My friend's book is a fantasy/romance/adventure genre.