I enjoyed the film so much I read the book. The book itself is unfinished and has two snippets at the very end that are disconnected from the rest of the work. It must have been very difficult to write a feature-length screenplay from this book. Not only is the book relatively short (200 pages about the size of a standard paperback with relatively large type), but there's very little "action." The book is all from Pierre's point of view, obviously (the title Ma Mère means My Mother), and it's mostly what he thinks about situations. The only characters in the book are the father, Pierre, Hélène, Réa, Hansi, and Loulou. (The grandparents are mentioned, just as they are in the film.) While the book addresses homosexuality, it only looks at the lesbian side of things because in the book Loulou is a woman. Nearly all the book content made it into the film, but there's much of the film that isn't part of the novel.