My first impression of Hitman's Guide was that Helgason has an indelible grasp of crude language. Nothing changed my mind.
However, I stuck with it for about a third of the book, pleased to find that the author has a sense of humor, one of the only saving graces of his writing. Another--the major one, and probably the only other one--is the main character's profession, hit man, which made me keep doggedly plowing through the sludge that is the author's use of obscene language.
To his (dubious) credit, he invented neologisms that would confound a sailor's lively powers of profanity.
I'm going to pass on reading any more of Hallgrimur Helgason's work.