We have many non-Brits here who may not understand all the cultural and historical allusions. And the books are famously challenging to read, after all Ford was a friend of James Joyce and used some of his writing techniques. 

Four books but the last one has not been included in the film. I recommend the e-book if you have a reader. There are quite a lot of obsolete words and military terms which I found in the dictionary. 
 

I read the book after having seen the film, first in e-book format, but then I just had to buy a paper copy, because it is easier to go back to my favourite bits. I loved it, especially the first volume, which is an absolute masterpiece. The second and the third volumes are also good, but the fourth one is far worse and it was a right decision to leave it out for the adaptation, IMO.
In any case, knowing that B. fell for the book and for his character, to read the books and then go back to the film is an utter delight. And he does love it and brings it up all the time.

Yeah they seem to mumble at lot, and Benedict is wearing things in his mouth to make him look fatter which unfortunately I think was a bad call. He already has to work around his lisp, working around those just made half his lines incomprehensible