Like it says in the foreword, the main story is told in the three previous volumes. This here are four shorts that fill gaps, or explain things.
The first is about the golden spider, and the first web (which was a very chicken and eggs thing that hurts your head if you think about it too much).
Second tells us about how Lucivar gets Marian in the gap between novel 2 and 3. Good romace.
Third expands on something mentioned in the previous short, and explains a bit why the two boys survived their lives. It's painful as fuck, and showcases exactly how thoroughly Saetan and Hekate misunderstand each-other. No, more: how unfathomable each of their natures is to the other.
Fourth is a continuation on the saga. Beyond the shenanigans, the most beautiful bit was that "there was one more dreamer", and all that it entails.