The Year of Magical Thinking can be compared to Didion's other non-fiction works, especially Blue Nights, which Didion wrote following the death of her daughter, Quintana. It could also be insightful to read the novels of Didion's husband, John Gregory Dunne, including True Confessions and Harp, which are featured in Didion's memoir.
Consider other writers' memoirs of grief, such as C.S. Lewis's A Grief Observed, Helen Macdonald's H Is for Hawk, and Meghan O'Rourke's The Long Goodbye.