Design Patterns: Elements of Reusable Object-Oriented Software

Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides; Addison-Wesley 1995. ISBN 0-201-63361-2.

From the Preface -- This book isn't an introduction to object-oriented technology or design. Many books already do a good job of that...this isn't an advanced treatise either. It's a book of design patterns that describe simple and elegant solutions to specific problems in object-oriented software design... Once you understand the design patterns and have had an "Aha!" (and not just a "Huh?" experience with them, you won't ever think about object-oriented design in the same way. You'll have insights that can make your own designs more flexible, modular, reusable, and understandable, which is why you're interested in object-oriented technology in the first place, right?

This book has been mentioned in the following pages of the Jargon File: Gang of Four.