Almost Wolfe-ian in its clamor of vaguely alluded details, any of which you fear you might need to remember later, in case they turn out to be lies. A whimsical universe that's purposefully forgotten its own history; possibly post-Oz, possibly post-human-engineering (re:Oryx and Crake); where pupil dilation is a creepy extinct ability and anyone can only see a narrow range of the visible spectrum in color, creating a hue-based caste system. The back matter implies the author did a bit of colorblindness research to get a feel for how things look with different types of missing hue perception, and it shows in the prose -- very compelling descriptions, a few neat hue-related puzzles. Fabulous mystery technology in a sort of mishmash of steampunk and deep future sort of way.

As Fforde gets better at knitting stories, his puns get worse. Like ya do. ;)

I look forward to the others!