LiNUXLiNKS.com has posted a list of their favorite free Linux books.
«Individuals wanting to learn about the Linux operating system have a large selection of books to choose from. There are many thousands of informative Linux books which are in-print and available to download or buy at reasonable cost. However, as many users are attracted to Linux for the very reason that it is available under a freely distributable license, some will also want this to extend to the documentation they read. The focus of this article is to select some of the finest Linux books which are available to download for free.«
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Don't fear the penguin 