I just finished Allen Holub's Holub on Patterns - Learning Design Patterns by Looking at Code. I highly recommend this book to all the software architects and senior software engineers.
This book is very condensed. It only has 4 chapters and 1 appendix. However, don't be fooled by the number of chapters. Holub is able to going thru all the GoF patterns just by using two software examples. The appendix is very helpful too. It summaries all the GoF patterns. It can be used as quick reference when working on software design.
You can order the book from Holub's website. If you want to buy the book from the other online bookstore, the ISBN is 1-59059-388-X.
BTW, you have to know about Java programming plus UML in order to understand this book.