Other works by Matt Haig include: The Last Family in England; The Dead Fathers Club; The Possession of Mr Cave; The Radleys; The Humans; and How to Stop Time.
For more novels dealing with parallel universes, consider: A Wrinkle in Time by Madeleine L'Engle; The Future of Another Timeline by Annalee Newitz; A Darker Shade of Magic by VE Schwab; Nightfall by Will Elliott; The Light Brigade by Kameron Hurley; The 10,000 Doors of January by Alix E Harrow; This is How You Lose the Time War by Amal El-Mohtar and Max Gladstone; Neverwhere by Neil Gaiman; The Shining Girls by Lauren Beukes; Mr. Fox by Helen Oyeyemi; One of Our Thursdays is Missing by Jasper Fforde; The Heavens by Sandra Newman;...