What do you value most in the books you read?

I started a discussion on my other blog about Cloud Atlas and the new film version, in which we’re talking about physical descriptions of characters.

And it got me thinking: what do you like best in your reading material? Great dialogue, stunning plot, relatable characters, poetic descriptions, societal importance, genre? Are you willing to forgive bad writing for a breathtaking plot? Will you endure laborious descriptions for magical fantasy? Do you wade through anything for romance? Do you hate fiction and value nonfiction?

What’s your thing in the books you consider great? And while we’re at it, what do you loathe above all else in fiction?