* The Star Wars movie novelizations: These are books that tell the story of the original Star Wars films, written by Alan Dean Foster. They were published shortly after the films' release.
* The Star Wars Legends series: This massive collection of books, comics, and other media expanded the Star Wars universe before Disney's acquisition. It includes various novels, like the Thrawn trilogy, the X-Wing series, and many more.
* The Star Wars canon novels: Since Disney took over, they have established a new canon for Star Wars. This includes new novels like the Thrawn: Alliances trilogy, the High Republic series, and the Aftermath trilogy.
* The Star Wars: The Force Awakens novel: This book tells the story of the seventh Star Wars movie, written by Alan Dean Foster.
To figure out which "Star Wars book" you're thinking of, please tell me more about what you're looking for. For example, what story are you interested in? Which characters are featured? Do you know when the book was published?