Books by author: Martin Fowler

UML Distilled is a fast-paced overview of the UML techniques for object-oriented software design. It was useful for me, as a quick-start guide for drawing some of the UML diagrams (which I plan to use initially for documentation of already-designed software, later for planning refactoring of existing code, and finally for design of new software applications). The book assumes a lot of familiarity with object-oriented concepts, so it's not the place to begin if you're just starting out with OO concepts.