Good question.

For one I enjoy the "complete" information a book presents. I like a full explaination on one players feel for the game and it really helps you to understand how others play. I feel that if a book has one usefull piece of new knowledge in it that will help me profit at poker than it will surely pay for itself. I don't think I have read a book yet that did not have at least one good point or two in it, although some do have less than others. Also if you havn't read a piece of information you can be sure someone else has, why not fill some spare time growing your knowledge?

Two might be a little wierd and has more to do with why I own the books than anything but I like to have a good solid archive. Books to refrence when I have stumbled upon some epiphany at the table and remember that "that guy mentioned that in that book." I can look it up and get differing views and possibly solidify a theory or idea I had at the table, or away from the table.

The main reason is that I just enjoy reading and there is little replacement for sitting down, getting comfortable, and reading a good book. Since I am into poker I like to read poker books. If I was into race cars I would read race car books and if I were into fighter jets I would read fighter jet books. I like to read and I work at a computer screen all day. I figure I kill two birds with one stone this way; I get to enjoy the relaxation of a book and at the same time hopefully improve my game!