What's your go-to comfort book? It can be a specific title, or even genre. For me as an adult, it's anything by Terry Pratchett. I don't know that he's a comforting writer, per se, but the worlds he weaves are inviting. Discworld is so big, I like the idea that I will never explore all of it. Somehow that notion makes me feel...interested and cozy.
I think another might be The Graveyard Book, even though it's a saddish book. It feels so full and is also exciting.
When I was younger, my comfort books were the Harry Potter series and the Hitchhiker's Guide books. Hell, giving those a re-read is a good idea now.
When I was small, it was The Farthest-Away Mountain and The Last Slice of Rainbow.
What are/were yours?