tl;dr It's a great book, and a must have for Werewolf storytellers as well as Shadow Gifts players will want to have access to. Most of the antagonists can fit well into other games, and there's links to Hunter, Beast, Contagion Chronicles, Mummy and other settings.
As a reminder you can check the preview link under the image of the book and see the first few pages (it usually starts at the table of contents, but the first page of that doesn't show).
Shunned by the Moon is part of the Night Horrors line, offering a variety of interesting antagonists and obstacles for Werewolf: the Forsaken. With a dash of Vampire's 'Wicked Dead' it doesn't just offer example NPCs but a lot of 'variant' antagonists that deviate from the standard (like spirits from outer space, Bale Hounds, and ghost wolf mutants or claimed), and a good-sized last chapter offering a ton of advice about running werewolf and specifically running it with the dominating theme of the hunt. Each of the tribal Sacred Prey are covered, as well as out of context threats like idigam and geryo. It's a surprisingly big book, too, 205 pages is about 40 more pages than the previous biggest books, and it is pretty packed with content. So at the least, you get a lot of material for the price.
The first chapter is really kicked off by the intro fiction, which depicts a Forsaken raid on a Pure facility with a lot of surprises coming from every werewolf involved. And the chapter expands and explains, we get the upgraded Pure ready for second edition, backed by their Firstborn totems and able to fight Forsaken on even ground through new Aspects, Rites, and Merits. Five new Gifts are made available (not limited to the Pure and really useful for Forsaken), those of Agony, Blood, Disease, Fervor, and Hunger. There's 3 example Pure, each turning the stereotype of their tribe on their head, I particularly liked the celebrity party girl Predator King who drives others of the idle rich and famous to obscene acts of savagery. The next part updates the Bale Hounds to 2e, with 5 Maeljin disassociated from the 7 Deadly Sins and instead focused on subverting werewolf culture (though they can be targeted towards other enemies), these guys are pretty nasty, and develop physical mutations as they grow in power, complete with 3 example NPCs of different levels of corruption, ranging from prospective recruit to Envoy of Soulless Wolf. Lastly there's a group of sort of ghost wolf 'mutants,' which show some of the downsides of not being anchored to a Firstborn, including the Tyrants who become sort of a domineering pack totem for the herd of humans they oversee, Devourers who get obscene powers via the consumption of werewolf flesh, Void Reivers who are infected by spirits from the dark reaches of space, and Mimics, arguably an evolution that doubles down on the shapeshifting of werewolves to create predators without codes or honor or restraint. There's also the titular Moon-Shunned, who through quirks of fate are born without Auspice and invisible to Luna's light.
The next chapter focuses on Spirits and the Shadow. The first spirits we get lean towards the more powerful and high ranked, but all have good reasons to run into werewolves, whether because they hate them or because their normal activities might upset territories. There's even a Lune, a Maeltinet, and a Secondborn (their backstory ties in to that of Task Force Valkyrie, from Hunter). The middle of this chapter focuses on oddities of the Shadow, specifically Wounds (offering many options for how they might hinder those inside, but also how werewolves can heal them) and void spirits, alien spirits from beyond Earth's atmosphere, like the aggressive Urinsahi from Mars, or the near-apocalyptic Skybreaker void leviathan. 'What about spirits from space' has been a popular question the last few years and this section does a lot to explore the answer and give some nasty surprises. The rest of the chapter is made up of Ridden and Claimed, ranging from outright destructive entities to those who are much more manipulative that may not even seem harmful at first glance.
Chapter three is all about the hosts. While it doesn't delve into the specific biology of them, there's four new types of host and each has a fleshed out example that can easily act as a jumping-off point for those who want to make their own Toad, Wasp, Termite or Lamprey hosts. Here we also see an established member of the Spider-hosts, and a Locust-host who has their own cult and wide area of influence. It would be great to have a lot more about the hosts I'm particularly happy with this chapter, each antagonist is fully fleshed out with their own abilities and motives that show what their hosts are like, and they offer a much more dangerous set of antagonists than the new hosts in the last Night Horrors for the game, Wolfsbane.
Then we get to the Herd, human threats. There's only three groups here but they offer some sideways looks at humans as prey, in that they are not out to actively ruin werewolf lives, but do the kind of things that can require werewolf attention. The first group, RD-13, has found some method to make gateways to other worlds, one of which is the Shadow. Unfortunately their understanding of these worlds is incomplete and there's a lot of seepage, leading to mutations of their workforce and 'things' running loose in territories. The second group is the Church of the Wolf, a modern religion created by people whose minds have been shattered by the effects of Lunacy, and seek out the entities they see as the descendants of gods (werewolves). Aside from seeking out werewolves they seem to be favored by Luna, and have some interesting tricks up their sleeves in the form of rites, the one we have mechanics for lets them force a werewolf to go on a sacred hunt on a target of the congregation's choice. The last group is one that's been wanted for a while as well, Shadow occultists, human shamans who gain the ability to use Influences and often pick up a patron in the form of Shadow entities.
The penultimate chapter, appropriately titled 'Nightmares' is where things get really nasty. This focuses on the things called out-of-context antagonists in the wave of second edition Chronicles, and things that hunt werewolves. It starts with idigam, offering a bunch of new powers for them (Forge Undead is a new add to Essence shaping that satisfies my idigam-as-zombie apocalypse yearning) and four new ones, including a particularly nasty and gigantic one that exists in the Gauntlet itself (along with some rules for how to enter it). Then enter the Geryo, a mostly new antagonist that debut in the Contagion Chronicle, they see themselves as alpha version examples of werewolves, and superior despite being sealed away by their creators. There's some crossover with Beast here, as while the Uratha were believed to be created by Father Wolf and Luna, Father Wolf is thought to have partnered with Beast's Dark Mother to create the Geryo, and there's some mechanical feedback that reinforces this. Ancient horrors that offer a more personal threat to the werewolves than the world-changing idigam, they are still hugely nasty entities, capable of infecting packs with their transmogrifying body horror contagion.
The last chapter, Commencing Your Hunt, is all about running the game. It offers a lot of ideas and advice to help storytellers focus their game on the predatory world of werewolves and get that mood across to their players. It starts with six different and customizable pitches that encompass the big events of werewolf life, from turf wars to the rebirth of Pangaea, including references to entities within the rest of the book that can be used for stories about these kinds of things. The next part of the chapter focuses on the setting, neatly encapsulating a lot of first edition's Territories in a series of easy to crib charts that can help storytellers flesh out their setting while also offering ideas for how to portray it to their players. As a long time Werewolf storyteller and player I've seen a lot of people struggle with how to get started and this chapter really helps people along with that, it's good for those new to the game as well as more experienced storytellers. It's easily worthy of being in the core book.
All in all, it's a great book. Mixing the flavors of the two kinds of Night Horrors books, by offering 'types' of antagonist as well as specific examples lets people plug and play antagonists as well as offers a bit of blue prints for those who want to build things themselves. All the sacred prey are covered, and often range in 'difficulty' from annoyances that aren't quite threat enough to be killed to Final Boss, as well as out-of-context threats for just about every one of those used to their 'standard' sacred prey. Players aren't left out, with new Gifts and enough mechanics and ideas to offer options for those who want to play Pure or Bale Hounds or mortal Shadow Shamans, while still expanding options for regular Forsaken. Even for those who primarily run other lines there's plot hooks and antagonists that can easily fit in (nearly every game is susceptible to claiming, or is going to be upset by the presence of some of the creatures within), with some even being fitting for mid-to-high end Hunter the Vigil targets. The only real negative thing I can say about the book is that it doesn't spend a lot of chapters detailing the intricacies of monster culture and society, though the telling glimpses seen through the antagonists, story hooks and rumors go a long way.
I wanted to add this. I'm not an art guy. Most of the time I don't look at it much unless it stands out (I have a couple of the posters). I don't have an easy way to read these pdfs beyond my desktop, my e-reader doesn't do pdfs well and I usually end up just copying the text so when I re-read it its without images. But I do do my first readthrough via the pdf itself and I really liked the images. I think some of the artists are new (the photorealistic Shadow Occultist art seems different from the realistic figures of the Pure characters). Regardless, I like it, and especially with the alien and monstrous things I think they did a good job.