I have several favorites in common with those already mentioned.
Ferdinand, which I loved as a child, which I bought for my daughter when I learned her school did not have it. She was in junior high when I became aware that she had never read it, but I got it anyway. She likes it.
Ramona and Beezus are good.
Junie B. Jones are fun stories.
Some of the Dr. Seuss books qualify for the ability to draw the imagination and adventure to children, and even to help their parents remember the joy of fantasy.
Judy Blume is one of my favorite children’s authors. She does exactly the opposite of Seuss in that she puts some of life’s difficult realities into the safe environment of a story, so children can have a medium for searching their feelings and accepting difficult situations. I know that she was personally responsible for educating numerous preteens about puberty, and some myths dispelled, with Are You There God? It’s Me, Margaret. Back when most schools were failing to teach about physical changes, kids were picking up the book and passing it around. I read it when our school library had a two month waiting list. A friend of mine let me read it while she had it checked out so I wouldn’t have to wait so long.
Judy had the nerve to present facts and myths in gentle form when most grown ups whispered to each other and wouldn’t talk with their kids much at all.