I think that most readers of children's books would agree that Rosemary Wells is a truly special author/illustrator. Her books are funny, warm, and appealing to both girls and boys. Max and Ruby are great characters and their relationship is one shared by many siblings.
My favorite gift to parents of 3 and 4-year-olds is the box set of the Bunny Planet books--Moss Pillows, First Tomato, and Island Light.
These books are so special because they show children that bad days do happen and that they are still loved even when parents and others are frazzled.
In Moss Pillows, for example, poor Robert has to visit his Uncle Ed and Aunt Margo. It is not a good day:
"Ed and Margo's four boys all piled on top of him at once. Just before dinner Ed and Margo were bitten by the argument bug. Dinner was cold liver chili. All evening Robert had to hide from the boys."
When the Bunny Queen Janet tells him, "Here's the day that should have been," Robert has a wonderful day in the green woods all by himself. He plays music and has a tree house. Everything is simple and beautiful.
"The kitchen is my favorite room. It's easy to keep it clean. I have a secret recipe for toasted tangerine. Place the sections on a log, directly in the sun. Wait until they're warm and crisp. Eat them when they're done."
Such a nice counterpart to the uncouth relatives with (from Robert's only-child perspective) too many children. I hate the word "crisp," but Rosemary Wells I'll forgive anything.