What makes a fiction best seller?

^ I always thought immersion was the biggest factor. To me, a lot of "high-brow" fiction is not hard to read, but simply hard to care about. Some authors are, it seems to me, more concerned with an intricately polished masterpiece that's literary and intelligent than telling a engaging story. It's like they're keeping you away at arm's length. With stories like Harry Potter, you feel like you can just step into that world and muck about.
As for Twilight, I'm not a fan but I can understand why it's so popular. There's a raw energy and honesty that makes it a bold change from many books.

 

Sometimes less is more. Some people, although they could use the money, see themselves primarily as artists rather than entertainers. The last thing they want is for people to 'muck about'--they seek to provoke a more intelligent reaction.
Of course, let's not be too elitist--there's nothing wrong with giving people a fun read. If writers are really great, they may reach the pinnacle and become truly great artists AND entertainers. We can dream *sigh*