Medieval Iceland is fascinating to me. They had a government which almost approaches the modern Libertarian ideal in terms of its structure (less so regarding the substance of the laws, see below). This fascinating volume brings the structure of medieval Icelandic law to life, allowing a new generation of scholars and medievalists to appreciate and understand the legal code of this important civilization.
This book covers basically four topics: Christian obligations, legal procedures, assault and homicide, and the structure of the legal authorities (Quarter Courts, the Lawspeaker, the Law Council, etc).
The section on Christian obligations is important in part because of how it sheds light on the medieval Christian church in Iceland, but is also important in terms of what heathen practices were banned. The fact that going berserk was banned in a list along with worshipping heathen idols is thus somewhat significant and reinforces the idea that this was a cultic practice. Similarly the idea that pigs could not eat horse flesh and then be eaten by humans is probably an indirect reference to pagan horse sacrifice.
The bulk of the book is devoted to legal procedures and to penalties for not following them. For example, it's worth noting that the penalty for assault with a deadly weapon (assuming no battery occurs) is the same as the penalty for not baptising child, or for baptising a dying child incorrectly, and these are also equivalent to refusing to show up for jury duty, failing to show up as a witness, and so forth. All these offences carry the penalty of lesser outlawry (basically something sort of like house arrest for three years).
Moreover the system has a remarkable set of checks and balances built in. While a jury can convict on a bare majority (or an even split along with a chieftain), this has a set of remarkable features, such as the existence of "clearing verdicts" by a smaller panel of jurors. Consequently my reading is that to secure a conviction one must obtain majorities on two juries, the first being a five-member panel of the neighbors of the accused, and the second being twelve uninvolved individuals. In the even that the jury of twelve is evenly split, the chieftain can either offer a verdict or send it to a special secondary court (the fifth quarter) which seems to hear primarily procedural cases (false testimony, failure to appear as a witness, failure to appear for jury duty, failure to appoint jurors, and the like).
Anglo-American law owes a surprising amount to the same Viking-age Norse legal structures that gave rise to this system. Hence this provides a fascinating view into an alternate development of one of the roots of Anglo-American law, as well as the sagas, medieval history, and so forth.