"Mordet på maskinbygger rolfsen" by Maurits Hansen.
not a overly long book, but the language in that book was kinda hard to follow.. especially since i had to look up al the german, french and latin words he used.
it's on of the first crime stories ever written by the way, it was written before "Murders in rue morgue" by Edgar Allan Poe. (I like Poe's story better though

)
The reason the book was hard was just the old language used in it i guess. if i were to pick up a newer translated version of the book it would probably have been a lot easier. : p
Also noticed some people were putting forth bad books here, and well i have one i nearly gave up on (would have if the other ones were not really good books..) and that is "The land of mist" by sir arthur conan doyle. The professor challenger stories were so great, then i picked "the land of mist" up and oh my god, it was bad. o.o' It kinda estroyed the character for me when I read the last 2 professor challenger stories: "the day the world screamed" and "The disintegration machine", which both were pretty awesome.