monograph; standalone book
Refers to a single, self-contained book on a specific subject, as opposed to a volume in a series or a journal article. Often used in academic or library contexts.
This research was published as a monograph.
I looked for a standalone book on that topic in the library.
Compound of 単行 (tankō, 'independent publication') + 書 (sho, 'book'). The exact historical derivation is uncertain, but the term is conventionally associated with scholarly monographs.