My baby (10 months old) loves Lois Ehlert's vivid collages. He really enjoyed Red Leaf, Yellow Leaf with its crumpled tissue leaves and real tree tags along with charming representations of people, trucks, etc. For the adult reader, there is subtle humor in the inclusion of what look like real tags from trees, and the attribution of homesickness to the tree (just when it was getting settled in, they dug it up and took it to the garden center...). Older children just learning to read will probably get a kick out of the inclusion of "hidden words"... tiny scraps of text set right into the pictures, saying things like "bird treat" and "squirrel"... There's even a recipe for the bird treat in the back of the dust cover!
This is a great little book describing the annual life cycle of a maple tree. There is a very easy to understand description of why leaves change colour and some nice ideas for activities at home at the end of the book. The use of colour is excellent. My 2 and 4 year olds love it.