Do you read math & hard science books? How?
plinkplonk: In my student days, before I became a working programmer,  I was desperately poor and couldn't afford all the books I wanted to buy. So I got into the habit of buying books when I had money in my account to avoid a future in which I have to look longingly at a book and not have money to buy it. So, yes your "buying a book and reading a few years later" situation is something i am familiar with.So anyways, I ended up having a few hundred technical books (and a couple of thousand non technical books). The future of not having money to buy books never came (yet, touch wood) and the biggest advantage of having this huge collection of books is I can cross reference them to get better info on what I am looking for. On the other hand, moving is a huge pain :-)EDIT:(example of buying a book and then using it years later)  I am now (slowly) working through Cormen et al's "Introdcution to Algorithms"  (second edition) book. The idea is to do all the exercises and proofs and so on. Should be done by the end of the year I think.I bought this book a  few years ago and am using it(seriously) only now. (There's a third edition out now for anyone planning to buy. second ed is good enough for my purposes)