Paperback, I don't feel comfortable with hard covers, feels like I actually need to find a position to read, it doesn't feel natural. That makes for:

 Paper 10 x 9 Hard

Also, I detest the way books are made in the United States. They feel too disposable, in fact, a newly print book will take only a matter of months to age and yellow. It's like those books are meant to be read once and disposed of, I don't like that; I prefer durable paper in which I can write and to which I can return years later ;)