One thing I always wonder when watching The 13th Warrior is, how Ahmed learns the Norse language so fast. While I for myself could make some sense out of certain words, it must be significantly harder for an Arab to learn to speak it that fluently by merely listening to his Viking fellows for the time of their journey, be it even such a well-read man as Ahmed.
I of course understand that the time they are traveling and when he learns the language is longer than depicted and that the movie needs them to speak fluently with each other to forward the narrative (and his learning procedure hasn't been depicted too bad), so I don't have any problem with accepting this plot element as sufficiently plausible. Yet I still would like to know if this part or Ahmed's following conversations throughout the movie are actually true to the novel or in which way they might have been altered to a more movie-friendly narration, or if there is at least some information how long it took them to travel to King Hrothgar's court and Ahmed to learn the language.