Recently I saw an Ignite Boise presentation from a woman who read 200 books in one year. Many of these were classics. You may be interested in some of the classics in computer software. Classics do tend to become free eventually. Here are some good ones:
- Structure and Interpretation of Computer Programs, Abelson and Sussman
A look at the fundamentals of computer programming, most importantly that programs are data, and data can be programs. - On Lisp, Paul Graham
A great look at why Lisp and other higher order languages are the future, not the past of software development. - Higher-Order Perl, Mark Jason Dominus
Higher order programming implemented in the original Swiss army knife of computer languages, Perl.