I'm reading Harry Potter et la Coupe de Feu (Harry Potter and the Cup of Fire, en français) at the moment (along with various textbooks).
One cool thing about reading it in French, is that you learn all sorts of useful (and useless) words, such as "Moldus" is the French word for "Muggles" (which is a made up English word).
Some of the more useful words that I've learned are:
louche - shady, shifty, fishy, suspicious (chelou is the verlan)
pêle-mêle - any old how
la pacotille - cheap junk, trash, showy stuff
glousser - to chuckle, cluck (péj.)
narquois(e) - sardonic, mocking, derisive
échevelé(e) - wild, frenzied (i.e. hair)
brouhaha - hubbub
maussade - glum, gloomy (avoir l'air...)
effondrer - to gobble up, gulp, wolf down, engulf (bouffer)
une lubie - fad, hair-brained idea, craze