Another thumbs-up review, this one from the Washington Post. It's spoiler-heavy, so beware before you click through.

Kaufman, of course, is the clever one here, and he has a blast tweaking toxic masculinity, celebrity worship, political correctness, filmmaking, therapy, high art, low art and much more. Themes that have long preoccupied the writer, particularly in the films “Adaptation” and “Eternal Sunshine of the Spotless Mind,” reappear in “Antkind.” Humanity’s ever competing perceptions of reality, the unreliability of memory, the question of God’s existence and the malleable nature of storytelling are measured again and again in this novel that is long but never dull.

[...] But for all the absurd digressions and circuitous detours, “Antkind” remains propelled by Kaufman’s deep imagination, considerable writing ability and bull’s-eye wit. (Source)

Meanwhile NPR gives the book a more even-handed (and spoilerish) review:

Antkind is strange, disjointed, and obsessive. [...] You could call it a brilliant piece of metafiction or a marvel of postmodern storytelling and you'd be right — but you could also call it bloated or a flashy, eloquent mess and you'd also be right. Ah, subjectivity.

[...] The one thing that can be said about this book with certainty is that Kaufman is a master of language. He shows this time and again throughout the 750-page reading experience that is Antkind. His sense of humor injects many passages with a unique electricity that makes them memorable and the characters, cultural products, and events he's created speak volumes about his seemingly endless imagination.

[...] Antkind is a bit overstuffed, but we all overstuff ourselves at a buffet once in a while. What matters is this is that this is an entertaining, unapologetic book that never steers clear of — well, anything. And watching Kaufman recklessly throw himself at everything with a backpack full of words is a sight to behold. (Source)