First of all, let's get our semantics straight. A novel is a book. But a book isn't necessarily a novel. It may be either a novel or a nonfiction work. The word, "book," simply refers to some form of literature that is "long form" rather than a short story or an article, for example. As for a play, that could be either a screenplay or a stage play—the former written for film and the latter for live theatrical performances. We won't even get into other types of scripts.
Regarding the differences between a novel and a script (or play), the most obvious is length. If you take an average-length book of 300 pages and adapt it into a screenplay or stage play (there is very little difference between the two except in the directions and a sense of the audience which is either watching live or watching on film), you cut, shorten, and tighten the novel down to roughly 90 pages. If you take a script and adopt it into a book, you have a MUCH tougher job. That's because you have to add not only words and pages to reach typical novel length but also effective descriptive passages, expanded dialogue, additional action, numerous subplots, and (most importantly of all) IMAGERY!