This paper does not aim to give directives on how to write reviews. Rather, it sets out to describe their position in the space of scientific discourse and to offer some guidance on the aspects of a text that should be taken on board prior to writing a review. After an introduction to some features of scientific texts, this paper describes the specific functions and objectives of book reviews (and more generally of critical reports on scientific texts). It then lists some criteria and questions aimed at raising the awareness of scholars who need to write such reports or synopses, and analyses a small corpus of book reviews to illustrate strengths and weaknesses found in such reports.