The Sworn Book is unlike the other Solomonic material in what it is for. Most operative grimoires promise knowledge, treasure, favour or power over spirits. The Liber Juratus opens by promising the beatific vision, the direct sight of God, and it treats everything else it contains as subordinate to that.
The method is a long ritual programme, running to weeks, of confession, fasting, prayer and the recitation of divine names, culminating in the operation with the great seal of God, a complex figure the text describes at length. Only after this does it turn to the angels of the planets and of the airs, and then to the spirits of the earth.
That structure is the book's defence. It is framed by a prologue describing a council of magicians assembled in response to persecution, and the argument it makes is that the art is a religious discipline whose highest end is the same as the Church's. Whether that framing is sincere or protective is not settled, and it hardly matters to how the text reads.
The oath the title refers to restricts copying and transmission, which is one reason few manuscripts survive.
Fewer than a handful of medieval manuscripts of the Liber Juratus are known, and they differ in the seal and in the order of the material, so what the original looked like is genuinely uncertain.
The book is also the earliest Western text in which the whole apparatus of ritual magic is defended as compatible with Christian devotion rather than merely disguised as it.