After Frog and Toad and Little Bear, my kiddo really enjoyed these books as a next step (I tried to list these from easiest to harder but it’s probably not perfect):
– A Toad for Tuesday, by Russell Erickson
– The Bears on Hemlock Mountain, by Alice Dalgliesh
– The Hundred Dresses, by Eleanor Estes
– Courage of Sarah Noble, by Alice Dalgliesh
– A Lion to Guard U, Shoeshine Girl, or others by Clyde Robert Bulla
– The Boxcar Children (just the first one) by Gertrude Chandler Warner