Kae Verens recently posted a book review to his blog about the Packt publishing book "Mastering phpMyAdmin 3.1" and describes how the book is different from its predecessor (covering phpMyAdmin 2.11).
There are many reviews of this book already, so I will mostly describe how this edition is different from the previous one. In short, though, I would say that this version is much more readable, and is still the best book to buy if you want a book on phpMyAdmin. The reviews I've read here all agree with my own assessment that phpMyAdmin is a surprise '" right when you think you know what it does, a book points out a load of stuff you didn't know it did.
He breaks it into two sections - the things that have gotten better (like the removal of some unneeded items and he inclusion of some of the more minor features) and some things that, unfortunately, have not improved (such as the increased size of the table of contents and the addition of other, too large screenshots).