The "Warriors Series" is a popular collection of children's books written by Erin Hunter. The series follows the adventures of wild cats living in clans in a forest setting. Each book features different characters and storylines, focusing on themes of friendship, loyalty, and survival. The series began with the first book, "Into the Wild," published in 2003. Since then, it has expanded to include multiple arcs and spin-offs, introducing readers to various clans like ThunderClan, RiverClan, WindClan, and ShadowClan. The books have gained a dedicated fanbase and have inspired graphic novels and a range of merchandise.