Different versions of "Mac OS X for Unix Geeks" (print vs ebook)?

There appears to be different versions of the "Mac OS X for Unix Geeks" book.

The 4th edition of this book -- http://shop.oreilly.com/product/97805... -- appears to be the latest printed version. Apparently, it was published in 2008, with an ebook version available since 2009.

However, there also seems to be an alternate ebook version available, published in 2011 -- http://shop.oreilly.com/product/97805.... While this would at first seem to be related to an earlier printed version of the book, it also appears that this might be a newer version than the 4th edition.

Can you please tell me which is the latest version of this book, and what are the difference between these two ebooks?

1 person has
this question