Happy New Year, everyone!
They belong to a category that I would call "metafiction"-- i.e. fiction about fiction-- but that the author himself places in a category called "speculative fiction." Inside the book fiction is a continent divided into countries such as "Racy Novel" and "Science Fiction" with surrounding islands like "Vanity" (i.e. self-published). The story centers around the politics in the fiction landscape and parodies modern day England.
I very much enjoyed One of Our Thursdays is Missing. It was entertaining and kept my mind off of other matters. I would recommend the series to anyone who enjoys Douglas Adams style humor with a literary bent (although make sure you've read a reasonable chunk of classics otherwise its not very funny). The one problem with the series is that the mythology is inconsistent. Fforde does not seem to care about consistency, sometimes even from chapter to chapter, e.g. how to book jump, the process of writing (interfacing author and ideas in the well of lost plots), generics, etc. However, there is something so charming about the writing style and something ridiculous enough about the world that it really doesn't seem to matter that much even to me (mythology is the big thing that excites or bothers me in a novel). I think part of it is the humor; the audience appreciates the joke more than the mythology.
I will attempt to post more regularly as my schedule gets back to normal.