"The Tale of Miss Tiggy-Wiggle," by Beatrix Potter, which is surprising, I know. I was expecting a rabbit story too.
All of the Brambly Hedge books by Jill Barklem, especially the Spring, Summer, Autumn and Winter Stories.
"Tales from Watership Down," by Richard Adams. The original book didn't make it on the list for some reason.
"Lucky and Squash," by Jeanne Birdsall. This one also surprised me, because it is a dog book but a glorious one at that.
"Wuthering Heights," by Emily Brontë, because that was one of the first books read aloud to them.
"The Little Prince," by Antoine de Saint-Exupéry.
"The Complete Tales of Winnie the Pooh," with particular attention towards "Eeyore Has a Birthday," by A. A. Milne.