As for favorite style of books, I prefer paperbacks. I don't really mind the type of paper on the inside, but it really bugs me if the pages aren't printed in line with the edge of the paper, or if the pages have the kind of edges that aren't even... Like this:

The pages have to be even for me, otherwise it drives me nuts and I can't get into the story enough to enjoy it. Because I fumble the pages. I don't reread books in their book form, so I don't usually have a problem with them falling apart. (usually, depends how many days they get shoved in an overstuffed backpack). When I want to reread a book, I get it on audio book, then I can listen to it when I can't actively read (when I'm driving for example) and read a new book when I can do the reading. I don't like most books with pictures in them, though there are a few that have occasional images that actually work well (meaning they are right).
As for cover art, a good cover is excellent and eyecatching, and certainly plays a part in first catching my attention in a store or library, but it isn't the most important part in my mind. But so does the title and the fact that it is sitting in a section called "Science Fiction" and/or "Fantasy". Or if it has recommendations from friends/family/real people somewhere (like you guys) who say it is good that aren't the ones printed on the cover/back, because those are just fluff (every book has them, it doesn't mean I will like every book). I also don't like cover art that depicts the characters, because I like to imagine them myself, and if they have them on the cover then I can't. Things that are more about surroundings, like if the book is about dragonriders and they have a vaugely human figure on a dragon, but you can't tell much about the characteristics of the person. More about a place, object, or action than a character's features.