Those who are interested in the history of law could do much worse than to read the letters of Pliny the Younger*. The second century Roman lawyer and magistrate’s letters are still preserved in near perfect form; the most famous of these is Epistle #10 to the Emperor Trajan.
Written in 112 C.E. – aka A.D. – its primary interest to most historians is that it’s the first written mention of Christians outside of the Bible (and the Dead Sea Scrolls, and the non-canonized Gospels, etc. – in other words, the first “pagan” reference). Pliny asks Trajan what he should do: should he execute these pesky Christians whose crimes don’t include any sort of rabble rousing or trouble making but simply refusing to worship correctly?