noun
new book; newly published book
Literal use for a new book or new publication. In many modern contexts 新刊 or 新刊書 is clearer for this meaning, because 新書 often suggests the paperback format.
その店は古書だけでなく新書も扱っている。
That shop handles not only old books but also new books.
noun
shinsho paperback
Publishing-format sense, referring to a small paperback size also called 新書判. Common with nonfiction and general-interest books sold in series.
See also: 新書判
通勤中に歴史の新書を一冊読んだ。
I read a compact paperback on history during my commute.
このテーマなら、まず入門向けの新書を読むといい。
For this topic, it is a good idea to start with an introductory shinsho paperback.