expression, noun
some book; a book on the subject
Used when referring to an unspecified book, often implying that the information is found in some written source. The phrase 物の本によると is common.
物の本によると、この植物は薬になるらしい。
According to some book, this plant is said to be medicinal.
expression, noun
General plural sense, often used in a slightly literary or old-fashioned way to refer to books collectively.
彼は暇さえあれば物の本を読んでいる。
He reads books whenever he has free time.
Compound of 物 (もの, 'thing') + の (possessive particle) + 本 (ほん, 'book'). The exact historical derivation is uncertain, but the phrase has been used since at least the Edo period to refer to books in a general or unspecified way.