Café Bibliothérapie discussion

Hello, I discovered bibliotherapy a few weeks ago, and I have many questions about it.
My first (and, I think, most important) question is : I see how I can decide to read this or that book because I have read it before, and I know what effect it will have on me; however, how can you know someone enough to know which book will have the desired effect on them?

Thank you very much for taking the time to read this post and answer it !

This question is actually what my research is about. It depends on what you are trying to accomplish. Genre seems to be important and depending on the condition, certain books do better than others. YA or problem novels do well when confronting a certain issue and finding one that mirrors the same situation that the reader is experiencing is good. Cognitive repair can occur using different genres that focus on Theory of Mind (ToM). ToM is the ability to be empathtic and predict what people are thinking/feeling. Some say mystery novels are good for that. Others say literature. Most important, however, the reader has to want to read the book. Does this help?

Thank you for your answer Peter, it's a beginning ! It looks like a rather long process, the best may be to have some kind of list in mind, and checking or not the titles depending on the person, with the final choice being theirs... It also means that you can only recommend the books (novels, poetry or otherwise) that you have already read and studied, does it not ?