I bought this book after going to the American Museum of Natural History in New York and wondering, "Why are dinosaurs so big?" Christopher McGowan didn't exactly answer my question, though he gave insight into the advantages of gigantism in general (greater relative energy efficiency and less relative locomotive costs). But McGowan offered a number of insights into both dinosaurs and animals in general that taught me a lot. I especially enjoyed his comparison of the advantages and disadvantages of warm-blooded versus cold-blooded.
Most importantly, the book gave scientific backing to a theory I've argued at least a few times, tongue in cheek: that elephants are a really boring animal to observe.
Here's what he had to say: "Elephants resolve much of the problem of supporting such a large body weight through their behavior. They live unhurried lives and seldom do anything quickly. They walk rather ponderously, keeping their legs relatively straight throughout, and though they can run at a fair pace, easily outrunning a man, their speed is achieved by virtue a long stride, not by rapid movement. Their run is a relatively straight-legged amble and they unable to gallop. Nor do they go in for jumping, bounding, or similar athletic activities. And although wild elephants sometimes rear up on their hind legs to reach up higher into trees, and captive ones can perform some unusual feats at the circus, they do all these things rather slowly and deliberately."