Thisis a 2016 release from Paizo Publishing as part of its Pathfinder Player Companion series. The cover of this one is by Kiki Moch Rizky and, as is usual in this series, there are several authors.
This one is available as both a pdf and a 32 page softcover. I'll be focusing on the print version which is staplebound with thick covers. The entire volume is on glossy paper and in full color. The editing is generally top-notch and the artwork and layout are excellent.
The theme of this tome is shadows and darkness; more specifically it focuses on providing new options to characters who spend (or have spent) a lot of time in the shadows. It mentions some of the creatures you'd expect, but it's really focused more on what happens when races who normally live in the light must instead live in the dark places of the world.
Predictably, it starts out with an introduction which lays out most of what I said in the previous paragraph. It also includes the standard rules index for new rules in this volume. There are a handful of archetypes, about 20 feats, and about 20 other rules options.
The first chapter talks about alternate racial traits available to those who have lived in shadows or light. There are traits for each of the main races of the core rulebook and they are provided with both replacement traits and points for those using the point build system.
Transformed by Shadow covers new traits and feats for Fetchlings and provides new rogue talents usable by fetchlings and by other thieves and the chapter ends with a new archetype for fetchling rogues.
The next chapter is a bit of a reversal and covers the Wayang, creatures from the plane of shadow who are now trapped here. There are new racial traits, feats, favorite classes, and even spells. There's a new eidolon subtype called Shadow. There's also information on Shadow Ink Tattoos and a new path for Oracles: Shadow.
Transformed by Darklands introduces Dro and Half-Drow characters. It provides new racial traits, favored class options, feats, spells, and rules for Shadow as a bloodrage bloodline, psychic discipline, weapon blessings and subdomain.
Shadowy Archetypes provide new Archetypes for shadowy paladins, alchemists, and sorcerers with appropriate ability changes for each.
Fighting in the Dark provides some general and specific tactics for fighting in the dark. It ends up with a selection of magical items which provide light in a variety of ways.
The next few sections provide a couple of pages each on Shadow weapons, shadowy feats, magic items with a shadowy theme, and spells with a penumbral and a shadow theme.
I've never read a Drizzt book, so I may not be the core audience for this supplement, but that doesn't matter. I think a lot of people think about what it would be like to be a shadowy man from a shadowy plane(t), and this book gives you the chance to do just that. There are plenty of options for standard races to be just a little different than their light-loving peers.
I think there are a lot of neat ideas here and the book is nice and thorough with shadowy touches for nearly every class and every race in the core rulebook. If you want to be Drizzt or a medieval Riddick, this is your chance.