This is book number 1 in the Forest Friends series.
Reginald is kind-hearted rat and loves everyone - except ... rats Believing rats are unlikable, he doesn't realize that he is a rat himself until the beautiful newcomer to the area, Raquel, stops his heart when she enters the annual Autumn "Geese Flying South" party - and into Reginald's life. She tells him the truth about himself, and he learns that all creatures - including rats - are lovable.