I was prescribed this book for an MA I am about to start this September, though this was actually very convient for me as I have been meaning to read this for a while.
Essentially, this collection of essays are calvino espousing what he loves about some of his favourite authors and works of fiction. It's organised in a general chronological order of when an author was active (Homer before Hemingway).
The real joy that comes from reading this collection is the the unbridled enthusiasm Calvino has for the works he is reviewing. In one essay he goes back to a poet he had been taught in school and compares the poet's works to the misremembered lines that calvino has had floating in his brain since adolescence and endeavours to understand *why* exactly his brain changed the phrasing or the metre.
This collection has really opened me up to authors I never had a interest in reading, or even knew existed. So far I've bought a copy of Pliny the Elder's Natural History and have decided to try and get my hands on some of the works of Balzac, Ariosto, Montale, Francis Ponge, and Jorge Luis Borges.
One shortcoming is that the collection is entirely filled with male authors (unless I seriously missed something), however I'd most likely put that down to history being unkind to female writers, also this collection was not organised by him as its publication was posthumous.