This book contains valuable ressources for any Scarred Lands game and provides 40-ish pages of awesomeness.
Chapter 1 presents new races. The half-elf and half-orc both return, which is a nice throw-back to the previous edition of the Scarred Lands. The gem of this chapter (and the whole book) is the tiefling race, with 18 (if I counted correctly) subraces, each tied to the different planes of existence of the Scarred Lands. This is a great addition to the setting and fits perfectly well in the mythos (in fact, the existence of tieflings are hinted at in several books in the previous edition, so here we are). Each subrace has unique abilities that fit well for their plane of origin. Also, some of the art used here is superb.
Chapter 2 provides reference table to complement the DMs screen. Includes a very useful list of magic items from the Player's Guide and The Wise and The Wicked. Small bemol here, the table of the titans is far away from the table of the gods, and the list of nations doesn't include city-states. But having the list of nations with the list of languages spoken there is terribly useful for quick reference.
Chapter 3 provides conversion for two 3E adventures. This means new DC and skills for skill checks, new stat blocks for NPCs and monsters (around 10 NPCs and 10 monsters, including some converted from Creature Collections). The converted monsters seem well-defined and use very well the 5E monster framework, and some are among iconic Scarred Lands monsters (yes, I'm looking at you, spider-eye goblins!)
Chapter 4 provides 17 spells converted from Relics & Rituals, mostly to be used by the NPCs described in the previous chapter, as well as one true ritual. Iconic Scarred Lands spells (and favorites of mine) make their return, including the bloosdtorm, corpse armor, among others. Too bad there is no information about which class can cast these spells, but that can be easily infered by comparing with the old R&R or the 5E spell lists.
Overall, a great product that can be useful in many different ways! Highly recommended.