I would like to recommend two (2) Linux books that might be helpful to some of the people reading this mailing list:
(1) "Red Hat Fedora and Enterprise Linux Bible", by Christopher Negus. Published by Wiley. Buy the edition for the version of CentOS you are using. This book is very easy to read and is probably best for Beginning to Intermediate users. This is the book I reach for first. (Disclaimer: I wrote a review that was published in one edition of the book and I received free copies of two editions. I have also purchased several editions)
(2) "Running Linux", published by O'Reilly. This book is a classic and was recommended to me by an engineer at Red Hat. I have the 4th edition, but there is a later edition available. This book is a tougher read, but, it goes into things more deeply than the other book I recommend. Probably best for Intermediate and Advanced users. I've purchased 2 or 3 editions of this book.
There are probably many other excellent Linux books available that others can recommend, especially about specific topics. HTH, Lanny