Complex sentence: It is the third book in the series including two others: "Silverwing", and "Sunwing", with a fourth book in the series called Darkwing, which is a prequel to Silverwing.
Split into simpler sentences: It is the third book in the series including two others: "Silverwing", and "Sunwing". There is also a fourth book in the series called Darkwing, which is a prequel to Silverwing.