Thursday Next: First Among Sequels by Jasper Fforde.
It's been a long time since the last Thursday Next book. Something Rotten was published waaaay back in 2004, and Fforde apparently put Thursday on hold while he published the two Nursery Crime books (The Big Over Easy and The Fourth Bear).
The story begins on Thursday's birthday. Although she dislikes celebrating her birthday, her husband Landen Parke-Laine has a gift for her before she leaves for her job at Acme Carpets, which is really a front for her old SpecOps department.
Landen is unaware that SpecOps hasn't really been disbanded, and the very complex plot of the book centres around what Thursday really does while Landen thinks she's installing carpets.
This is vintage Thursday Next. I've missed her and I'm happy she's back.