I just finished Matt Haig's Midnight Library. At first I thought it was going to be terribly depressing but turned out not to be. Nora's given up on life due to a series of disasters and ends up in the Midnight Library. Kind of a philosophical limbo in which she can choose from millions of books, filled with different scenarios to see what her life would have been like it she had made a different choice. She takes a multi universe trip, stepping into her alternate selves, trying on different lives.