Not novels that themselves are in the form of handbooks. There's a list of those on Goodreads. What I'm thinking of is a list of fictional handbooks as part of the story in fiction.
In Severance , Lumon has a Compliance Handbook for severed employees (that link leads to a lot of spoilers).
The Terraformers by Annalee Newitz has the Environmental Rescue Team Handbook, which the novel quotes from at the start of every chapter.