Another of Augustine's writings against the Pelagians, as many of his writings, are. This time it is about the Grace of Christ, that the Pelagians deny, other than in our capacity, and not in volition and action. This book sometimes borders to the inspirational and teaching of the true Christian view on this and sometimes less about the Pelagian view. The Pelagian writing excerpts here are quite a few, and Augustine elaborates it on many pages.
The second book here, "On Original Sin" is as the title hints considering the Pelagian view on original sin, if we are born with sin and if sin is present in the womb. It begins quite differently with reports from two synods where these things were discussed, one where the Pelagians were not condemned and the other where they were. After this initial reporting, Augustine turns to the arguments and the view of the Church, and goes on about it for quite a time.