I'm going to start by saying, I think I should have read Demigods & Magicians first. I think I got the reading order between this and that mixed up, but I will be reading that one next.
Upon opening the book, a note told me to put my "paw" on the cover, because finding the book alerted monsters. I did as instructed and nothing happened. 0/10, would not recommend. (haha)
The book is filled with short stories that are a few pages long, at most, which provide tips and explanations for new magicians, but some of them also seem like they're there just for fun. There are also quizzes and a couple puzzles about the gods. If you paid attention while reading the trilogy, they're easy. If you did not read the trilogy, go read that first. This is AFTER the trilogy.
In addition to the intended stories, there's an amusing overarching plot where Setne is reading the book and leaving notes about an evil plot. The set up for this made it clear to me that Demigods & Magicians should probably be read first, because Setne was never captured by the end of the trilogy.
Overall, this is a quick, fun read.