It is my understanding that the Icelandic saga's, for the most part serve as entertainment primarily, and then historical recordings. In Njál's Saga, ch 97 the institution of the Fifth Court (fimmtardómr), was created due to Njál's need for a chieftanship for his foster son, Höskuld. This saga also places this event before Iceland's Conversion to Christianity. In Reality, there is no further evidence that Njál played a role in the creation of the Fifth Court, and its institution is usually dated c. 1005, after icelands conversion. The merit for the this constitutional development usually is placed on Skapti Thoroddsson.

All in all though, most of the saga's that i have read are rather accurate and entertaining at the same time. I forget who said it, but some one related them to modern day made for tv movies in the states. I agree with this, but I am thinking that the sagas are more factual (depending on the saga) than most made for television Movies.