A feckless loser, likeable but kind of awful, has his life even further ruined by the intrusion of an SF/F trope. He joins up with a group of yet-more-awful guys and an cute girl or two; together they navigate a grody, nocturnal Americana fever-dream, overcome obstacles through randomised combat, and squabble interminably; a extensive range of graphics and atmospheric music rounds the experience out. Scatology, sass and geekery abound. If you've enjoyed previous Robb Sherwin games, then, this is a safe bet.
In Cryptozookeeper the subject is aliens and cryptids; the result is something that feels like The X-Files cross-bred with Pokemon, with an all-slacker cast. A lot of things don't make sense, and the general feeling is of a partial hallucination; wisecracking is juxtaposed with graphic horror, the plot develops tangled corners that you don't need to keep track of, and gameplay alternates between drifting easily along while expostulation happens, and being stuck in a frustrating corner with a skewy puzzle just beyond your grasp. And it's always night. And characters point out, repeatedly, the many aspects of the story that make no sense. It's a very particular kind of surreal.
At Cryptozookeeper's heart is a mini-game in which you create cryptids by combining DNA that you've collected, then battle them in an underground animal-fighting ring, in order to level them up to face a final challenge. The design is such that collecting all the DNA and discovering all the cryptids is optional. Combat is old-schoolish and random, but handled automatically and quickly; your main decisions are about gaining stats. On the other hand, you'll do a very great deal of it, it involves few strategic decisions, and it's not very clear how much is enough; players who dislike grinding may grit their teeth.
Thorough implementation is often talked about as a sine qua non of IF authorship, but it comes at a high cost. Sherwin puts as much effort, care and love into his games as anybody making IF, and does extensive testing; but robust implementation comes fairly low on his list. (Save often.) Among his higher priorities, it seems, is long-arc story. Cryptozookeeper is sometimes buggy or cumbersome, and often sparse and linear -- but it's also large and brim-full of content.
For much of the game you have three or four NPCs in tow, but you can talk to them rarely and on very limited topics. Despite this, they feel more developed than many NPCs with ten times their conversation topics -- Robb writes very well, the images help, and you have time to get to know them. (Too, you're constantly sniping at one another; the silences feel, appropriately, like irate sulking.)
Like most Sherwin games, this is basically about how the world is dark and horrible but even the most abject can be redeemed; it manages the difficult task of making both the darkness and the light seem genuine.