One test I have of a book is if it reads quickly, what is often called a "page turner."
A well-developed 3-D character can carry a good story or series. A foil is a good way to show off a 3-D character's growth and change, and the protagonist need not be the only growing character.
I like banter--not arguing--but personal exchange dialogue that shows how characters interact, because it is amusing to see characters mirror our own understanding of life truths (like cats ignoring you and what you do to attract her, for example, or the dialogue between Jeff Goldblum and Judd Hirsch in Independence Day; even stories told by Bill Cosby).
I like to watch a story unfold, and I consider many stories mysteries, even those of other formal genres. I like Sherlock Holmes because he noticed things other people around him didn't. That is very true to life.
When you get different experts together, you get insights into situations you don't get by yourself.