This is the English translation of the German game. It uses only the D20 system, as opposed to the original game that provided both its own Arcana system as well as d20 rules as alternative.
The book is split in two parts. The first half, Libellus Primus tells of the world that Engel takes place in. It details the events that have turned the Earth into the world it is now. It then continues to give an overview of the state of the world and it politics, followed by a detailed desciption of the Angeletic Church and the Engel. Finally, it introduces a couple of key characters and two Dreamseed (monsters), together with their stats.
The second half of the book, Libellus Secondus, deals with the game system. As Engel follows the D20 system, most of this is similar to other D20 core books, though there are of course Engel specific additions.
All characters in Engel are either a human or an Engel. Humans will be part one of the standard D20 classes: aristocrat, commoner, expert, fighter, rogue or warrior.
The Engel are divided in five orders, each of them a playable class: Michaelites (leaders), Gabrielites (warriors), Raphaelites (healers), Ramielites (seers) and Urielites (scouts).
In addition to the normal skills, the Engel have access to Potestates, supernatural skills that require the expenditure of hitpoints to use.