Matt Haig on ‘The Midnight Library,’ Mental Illness and Winnie-the-Pooh

Matt Haig was already several books into his career as a writer by the time he published “The Midnight Library” in 2020. One of those books, the 2015 memoir “Reasons to Stay Alive,” had even been a best seller in England, his home nation. Yet, “The Midnight Library” was a true breakout phenomenon. The novel, about a depressed woman who, after deciding to end her own life, ends up in a magical library in which every book presents her with an alternative life, eventually sold more than 10 million copies worldwide. The author’s new book, “The Midnight Train,” takes place on a paralle...