As a reader, I'm more likely to get a hardback. It just feels better/most familiar, and takes to all manner of impromptu bookmarks (strips of yesterday's paper, store receipts, etc.). When I have a book published, it'll most likely be an e-book. I doubt most of us will have a chance to get a hardback book published before the traditional publishing industry collapses. Still not sure how I feel about that, though.

I much prefer trade -- though I think mass market suggests deeper penetration into the market -- grocery strores, airports, etc. But trade is just more pleasurable to read -- the paper is usually nicer too.

In a bookstore with authors 'new to me,' I tend to buy their books if they're trade paperback (I found Henning Mankell that way).  If it's an author I like, I'll buy either trade paperback or mass-market.  If it's an author I love, I may buy anything from e-book to hardback.

 

My reality, though, is that I'm almost at the point of adding a room to the house because of books, so I'm trying to stick to borrowing from the library.