noun
outrageous book; absurd book; sensationalist book
A colloquial, often mocking term for a book that makes wild, unscientific, or absurd claims, typically in the realm of pseudoscience, conspiracy theories, or extreme revisionism. The term is strongly associated with the Japanese 'Tondemo-bon' genre critique.
あの出版社はトンデモ本ばかり出している。
That publisher only puts out outrageous books.
彼の説はまるでトンデモ本の内容だ。
His theory sounds like something out of a sensationalist book.
オカルト本 refers to occult books, which may overlap with トンデモ本 but lacks the strong connotation of absurdity or pseudoscience.
Compound of トンデモ (colloquial form of とんでもない, 'outrageous, absurd') and 本 (book). The term gained popularity in the 1990s through the work of critics who catalogued pseudoscientific and revisionist books.