Favorite “brain candy” book?

I (37F) was diagnosed with stage IV cancer last year and it's not responding well to treatment so far (still hopeful for a turn for the better). Couple that with the current state of the world and I've just been feeling really sad lately. What's your favorite fun, lighthearted, frivolous read? Looking to escape for a bit and don't want to be surprised by anything too sad or dark. I'm a relatively new reader and still figuring out what genres I like, so I'm open to anything! Thanks in advance.