Benton's very up to date book gives an overview of what is known about dinosaurs, in addition to their size and body plan. It also gives an accessible description of how what is known has been found out. He argues persuasively that large changes in dinosaur populations and and morphologies were more driven by external events, volcanic eruptions for example, than by simple competition with non-dinosaurs. He gives the reader the sense that paleontology has reached the stage of offering concrete reasons for what has been found. A good book.