Start of Darkness is a prequel story featuring the villains of The Order of the Stick (OotS) webcomic. It is the second “print-only” OotS book, featuring material not available on the website.
As with the other print-only collections, this trade is in greyscale due to cost concerns (except for a 9 page section in the middle).
Start of Darkness is 112 pages long, and features background on Xykon and Redcloak. It’s got light touches of humor, but is mostly a dark tale, as befits the embodiments of evil plaguing our heroes. Without going into spoilers, there is a TON of information here that gives great insight into the characters and their motivations.
Although I recommend reading all of the OotS books, I found On the Origin of PCs (Start of Darkness’s hero analog) enjoyable but not strictly necessary. In contrast, while like with Origin there’s nothing here vital to understanding the main story, there is great depth added to our villains here (particularly Redcloak) that shouldn’t be missed.
A fantastic side story to the central quest, Start of Darkness really is a must read if you’re following the main comic.
While the volume number -1 is appropriate from a “in-comic” time perspective, it doesn’t tell you when you should be reading this volume. As the author states in the introduction it can be read after Volume 2 without spoiling anything, but I’d recommend reading it between Volumes 3 and 4 (along with Origin, if you choose).