There are many valuable books freely available online. Some of these books are free as in speech, others are only free as in beer, and others are in the public domain. This page is a resource for finding some of the ones most interesting to me and people like me.

Note that many of the books listed here are also available in print. If you like a freely available book (that isn't in the public domain), I encourage you to buy it from the publisher. I have done so a number of times. It encourages more authors and publishers to release their books to the Internet. Having a paper copy can also be more convenient.

The following sites have a tremendous quantity of books. You could easily spend a happy lifetime reading them.

• O'Reilly's Open Books Project - As you probably know, O'Reilly has published a significant portion of the best technical books ever written. To me, the O'Reilly name on a book is a sure indicator of high quality. They place a special emphasis on free software and now have really shown their commitment to the developer community by releasing many books under open licenses (such as the GFDL).
• Network Theory Limited is a publisher of a number of books about free software. All(!) the books they have published are available under the GFDL. I recommend you give them a visit and see if they have any books that interest you.
• Project Gutenberg - Project Gutenberg is an excellent effort to preserve books that have passed into the public domain. They have archived thousands of books; if there is a classic book you want that was written before about 1923, there is a good chance you can find it at one of the ftp mirrors. Also, be sure to check out the Distributed Proofreaders subproject.
• FreeTechBooks - FreeTechBooks has about 130 (as of 12/31/03) technical books, references, and manuals. The resources are nicely categorized. FreeTechBooks has some books in common with other sources on this page, but many others as well. Focuses on free software.
• Andamooka - Andamooka hosts open content books for reading, annotation, and discussion. Think SourceForge for books. As of December 2003, they are hosting many technical books and a few non-technical books.
• Baen Free Library - The Baen Free Library also offers a number of books. They appear to be mostly fantasy and science fiction. Thanks to Stacie of quixotica.com for pointing this site out to me.

There are also many interesting books not in the above archives. I've locally mirrored some of the ones that permit redistribution in case they disappear.

• Structure and Interpretation of Computer Programs
• Eastern Standard Tribe [local copy]
• Down and Out in the Magic Kingdom [local copy]
• Out of Control
• Underground [local copy] (thanks to Tim for pointing this one out to me)
• Advanced Linux Programming [local copy]
• Linux From Scratch [local copy]
• The Linux Cookbook [local copy]
• Handbook of Applied Cryptography
• Open Source Development with CVS [local copy]
• Developing Applications With Objective Caml
• Programming Ruby