The genre no one admits is a genre
A publisher's press release is a document with one stated purpose and several unstated ones. The stated purpose: to inform. A book exists; here are its facts. The unstated purposes are more interesting — to position, to manage expectations, and, in the gaps between sentences, to quietly instruct reviewers on how to feel before they have read a word.
The form is almost liturgical in its consistency. An opening sentence establishes the author's seriousness, usually by invoking a previous book, a prize, or a country of origin. Then comes the descriptor — "luminous," "urgent," "unflinching," "searing" — chosen not to describe the book but to signal its register. A comparison follows, phrased with careful ambiguity: "in the tradition of" rather than "similar to," which would invite the obvious deflation. A brief, carefully decontextualized paragraph of plot. A closing sentence about the author's significance that stops just short of making a claim anyone could check.
What the press release never says is as legible as what it does. A book described as "quietly devastating" is probably not expected to move units quickly; the adjective "quiet" is publishing's way of saying be patient with this one. When the release mentions translation into seventeen languages before it mentions the novel's subject, you are looking at a commercial title dressed for prestige. When the comparison invoked is an author who died before 1970, the implication is literary seriousness; when the comparison is a living author with a large readership, the implication is something else, and the publicist knows it.