I bought a Kindle b/c I don't have room for all my books. I recently had a child and his books already fill one of my bookshelves. So I've been cleaning out my physical books, only keeping those I really like. The Kindle DX might be the way to go for texts. So you get unlimited space (Amazon will keep your books online), access to all the classics for free (via gutenberg,etc) and your books are always with you (while you carry the device anyway).

Of all the things you can spend your money on, books are the best investment by far.