Having worked with Tom for half a dozen years, I cannot claim to be an impartial judge, but I honestly believe that there is no better or more self-contained resource on finite elements than this book. While there are other solid, more specific books that contain material that this one does not (The Finite Element Method for Elliptic Problems by Ciarlet comes to mind, as does Ted Belytschko's Nonlinear Finite Elements for Continua and Structures) no other book stands as the single starting point for learning the subject. This is a practitioner's finite element book. A motivated novice graduate student with a gun to his head could write a working finite element code armed with only this book and a computer (ask me why I know this); none of the competing texts can make the same claim. The breadth of the book is also quite impressive. Many (embarassingly many) times as a graduate student I found myself at an impasse and was forced to ask Tom for help only to get the answer "I'm pretty sure that's fully worked out in my book." Without fail it was worked out there, fully and clearly. It is simply an excellent resource for anyone working in the field.
Great introduction to finite elements. Having started knowing nothing about them, the first few chapters of this provided enough information to code up a basic solver for incompressible Stokes from scratch. One of the few textbooks I've deemed worth buying lately.