From the intro to each entry:
Lovecraft created his various "shadowy congeners" because the stories of vampires, werewolves, and even ghosts had become too familiar and too formulaic to evoke true horror. Almost a century after he wrote, his own monstrous races have likewise begun to seem like comfortable story furniture rather than unnerving signals that the world is horrible and wrong.
Our goal with this series is to present a comprehensive look at Lovecraft’s hideous creatures, from as many angles as we can. Our goal is contradiction, surprise, and most especially the uncanny: the recognition of something familiar as something weird. As in the “Gods and Titans” section of the Trail of Cthulhu core book, this series deliberately contradicts itself, blurring boundaries and erasing certainties in the name of the uncanny. In your campaign, these variant truths might be misunderstandings, legends, heresies, or deliberate lies spread by the creatures to lull their foes into a false sense of familiarity.
Change anything and everything in these pages, most especially the ability scores. If you need a terrifying assassin, a brief but survivable fright, or a sanity-shattering horror, just add or subtract points at will.