I realized that, because I had bought so many books that had a dual Old French-Modern French format, I might as well just learn the differences and oddities, and the book that I've been reading, Old French by William Kibler, is just amazingly wonderful. The book assumes that you know modern French, Latin and general principles of linguistics and that you won't need to repeat crap with drills. It then presents aspects of Old French that are different from modern French from a grammatical standpoint, then from a syntactic standpoint, and finally it has a section at the end of each lesson about sound changes from Vulgar Latin, which really explains a whole HELL of a lot about how French got to be where it is.

I love the declension patterns, which aside from showing an intermediary step from Latin's five cases to the modern Romance lack of a case system for nouns also resolves some riddles. For example, "whore" became la pute in the nominative, but the oblique form was la putain (plural would be les putains in both nominative and oblique). Also, the move from /k/ > /tʃ/ > /ʃ/ for simple word-initial "c", explains how cacare became /tʃiakjer/ and then /tʃi'er/ and finally /ʃieʁ/, or chier, "to shit". The sound changes didn't just affect obscenities, but those are more interesting to write about than words like tela, which became toile. I guess the way li garz, "the boy", became le garçon in the oblique is interesting and non-obscene.

Anyway, I have the three volumes of the Pléiade Livre du Graal, their collection of the works of Chrétien de Troyes, their Tristan et Yseut compilation and their compilation of historical works from the Middle Ages (Froissart, Villehardouin et al.). I also have the Song of Roland and the Lays of Marie de France in crappier, non-Pléiade editions. Can anyone here (Larry? DomA?) recommend some other good works in Old French that would be worth reading?