A favorite series of mine, Mog in the Garden by Judith Kerr reminds me of books by Helen Oxenbury---in part because of the simplicity of Kerr's illustrations, as well as her ability to capture the everyday moments of childhood. As a boy and Mog go out into the garden they play in the grass, lie in the sun, splash through the rain...or at least the boy does, eat strawberries, climb trees, and smell flowers. At the end of the day the boy goes inside while Mog stays out to explore. The boy can't see in the dark so he stays inside but Mog always comes back. More adventures tomorrow!
Other books in the series include Mog the Forgetful Cat, Mog and Me, Mog's Family of Cats, and Mog's Kittens. There's also a boxed set of My First Mog Books.