If you are a programmer looking for literature on computer chess, then the Springer publishing company have just released a small treasurer trove for you. It seems that they have decided to drop the price of their electronic publications to $0.00 for titles published over 10 years ago.
Doing a quick search for chess I found a number of important Computer Chess titles including "Chess Skill in Man and Machine" and the "Computer Chess Compendium" and some newer titles (for me at least) like "Scalable Search in Computer Chess". Apart from the chess titles, there are publications that cover a lot of areas, and after I am done with chess, I will probably dive into the Number Theory section.
To find the books go to link.springer.com and search for Chess (or any other topic of interest). Books that you still have to pay for have a little padlock symbol on them but otherwise you can juts click on the download link and get them for free
(Thanks to Arjang Assadi for alerting me to this)