Books on Programming Theory?

subversionfactor asks: "I am a philosophy student with an intense interest in mathematics and programming. However, while I've always been able to find books about various experimental areas of mathematics, I've never seen (m)any on the subject of programming theory. Most bookstores' "Tech" sections only include how-to books and books about why dot-coms failed. Does anyone in the Slashdot community have any recommendations for books dealing with any aspect of programming theory?"