Complex sentence: It is the prequel and fourth addition to the Silverwing series, and takes place 65 million years before the events of the first book, Silverwing, describing the origins of the war between the birds and the beasts.
Split into simpler sentences: It is the prequel and fourth addition to the Silverwing series, and takes place 65 million years before the events of the first book, "Silverwing". It describes the origins of the war between the birds and the beasts.