It’s nice to have a basis for making refactoring decisions beyond “it just feels right”. Martin Fowler has compiled a great stack of proven design patterns and the logical reasons to employ them in an easy to follow format. I find his writing easy to digest as well.
While I’m a big fan of the Kindle, tech books with lots of code don’t do well on the small format screen. Fowler uses a side by side, left and right, method to compare a lot of the code in this book. If you get an ebook then be sure that you have a desktop/laptop to read it on. You’ll need the screen real-estate to make use of the comparisons.