If it wasn't clear, this sourcebook covers two alien species, the enigmatic Hivers and happy, funny, lethal Ithklur, each in great detail, with slight mention of some other Hiver clients and creatures. As such, it's a specialised resource, but particularly strong for what it covers in a philosophical, hard SF tradition. Some campaigns might not favour the Santa hats, jingle bells or "Blissful Warrior"'s personality from the Hiver section, though they build up to more subtle connotations than is immediately obvious.
Scan quality is mostly pretty good. Even a couple of pages with black text on a dark, complex background remain readable. The PDF is not bookmarked.
[4 of 5 Stars!]