The Secret Country (Eidolon Chronicles) by Jane Johnson
Description:Ben Arnold is an ordinary boy from an ordinary family. The only noticeable difference between him and any other boy his age are his eyes (one is hazel and one is bright green). When Ben rescues Iggy, a talking cat from another world, Ben's life becomes anything but ordinary. Ben discovers that his uncle Aleister and Mr. Dodds, a local pet shop owner, have been stealing magical creatures from their home in the secret country and introducing them into Ben's world. When Ben's mother falls mysteriously ill, Ben and his sisters are sent to live with their awful uncle and his awful family. Ben soon learns that his eyes hold the secret behind his mother's illness and the future of both worlds. Ben and Iggy must embark on an adventure to discover the secret and stop his uncle before both worlds are changed forever.