This is the book that got a lot of people started, me included. Some of the science in it is, shall we say, debatable; but its enthusiasm is infectious, and the love of all things dinosaurian seems to leap off the page. It jumps around cheerfully from subject to subject, taking in dinosaur anatomy, physiology, extinction and much more. The prose is easy to read and very absorbing, and perfectly complemented by Bakker's own beautiful black-and-white illustrations, which capture his vision of fast, powerful, active dinososaurs. I've owned two copies of this book, lent them both the ``friends'' and never seen them again. A classic.
Once you've read Heresies, you're ready for this superb compilation are articles by a wide selection of the top dinosaur workers. (Don't be put off by the cartoonish cover). It contains 43 separate essays arranged in six sections (The Discovery of Dinosaurs, The Study of Dinosaurs, The Groups of Dinosaurs, Biology of the Dinosaurs, Dinosaur Evolution in the Changing World of the Mesozoic Era and Dinosaurs and the Media), which can be read in any order. Each individual essay covers its ground in real detail, but explains its complex concepts with a minimum of technical jargon. A single volume that can take you from mere enthusiast all the way up to knowledgeable amateur!
(Along the same lines, you may wish to get Gregory S. Paul (Ed.), The Scientific American Book of Dinosaurs. St. Martins Press, November 2000. ISBN 0312262264. It's another compilation, similar in spirit to The Complete Dinosaur and more up to date, but much shorter, less comprehensive and less useful as a reference due to the absence of an index. Personally I have and like both, but if I had to choose one, then TCD would be the clear winner.)
This short and approachable book is a wonderful introduction to dinosaur biomechanics. It covers a multitude of issues, including mass estimation, athleticism, force calculation for necks and tails, estimating running speed from trackways, possible uses of crests, horns, etc. and much more - all in a way that makes its sometimes complex subject seem very straightforward. (If you like this book, you should go on to Christopher McGowan, Dinosaurs, Spitfires and Sea Dragons. Harvard Univ Press, September 1992. ISBN 067420770X. It covers many of the same areas but in more detail, and has much, much more to say about physiology, the mechanics of flight and swimming and - for some reason - ichthyosaurs. Outstanding.)
This is the big one. If you're ready for raw information, this is the best place to find it, and the closest thing to reading pre-digested primary literature. It's not cheap ($145 at Amazon.com) but it is as near definitive as any dinosaur reference work can be. It has all the key information on every genus valid at the time of publication, with lots of discussion, summaries of recent work, and some more discursive articles on the usual issues - metabolism, extinction, etc. Since the publication of the core volume, there have been three supplements issued so far, with a new one every year or two. These contain the core information on new genera and updates on important research concerning genera already covered in earlier volumes. I go back to these books more often than all my others combined.
So there you have it. My four-book introductory course on dinosaurs (or seven books if you include the Glut supplements, or nine if you also include the optional pair.)
Here are URLs for anyone wanting to buy these books online at either the American or UK Amazon stores: