Think about your favorite authors, your favorite books . . . what is it about them that makes you love them above all the other authors you’ve read? The stories? The characters? The way they appear to relish the taste of words on the tongue? The way they’re unafraid to show the nitty-gritty of life? How they sweep you off to a new, distant place? What is it about those books and authors that makes them resonate with you in ways that other, perfectly good books and authors do not?I love authors who write in depth about their characters, giving me at least a glimpse (if not the whole picture) of life from those characters' eyes. I love authors who constantly make me say, "Yes! I know exactly what you mean! I've thought the same thing so many times!" or "You're right. I've never seen things that way before, but now that I read this, I know you're right." I love authors who know how to make me smile-- even laugh. I don't mind crying a little, but for me to love a book best, it can't be one sorrow after another. I love authors whose descriptions are so perfect that I feel as though I'm living the story myself.
From time to time, I "visit" authors with a gift for readable poetic prose-- but more often I prefer a good sense of humor. Tight plots that keep the pages turning are good, but the books I love and return to on a regular basis tend to be slower-paced. (They're more character- than plot-based.) Books I love best are set in the real world-- though usually in another period of history-- and their version of "the real world" often comes with a few unrealistic bits.
I love books that are rich enough (in characterization, plot, setting) that they envelope me and melt away real life, for a while.
ETA: I forgot to answer the last part of the question!
I think the reason that some books with these characteristics resonate with me more strongly than others do lies partly with timing (meaning I first read them at just the right time of my life-- or that when I re-read them, I'm taken back to a pleasant time in my life), but mainly with the "recognition" factor. (The part above about "I know just what you mean!") If I find myself frequently "recognizing myself" in a book's characters or narrating voice, I tend to like it. It may sound conceited, but I don't think it's unusual. Most of us gravitate toward like-minded people. Why should it be any different with books and authors?