Margaret Wise Brown. I know I have personally read her classic book Goodnight Moon hundreds of times. I could probably recite it for you by heart, but will refrain.
Margaret Wise Brown led an interesting life and you can find out about her at her web site. She was a prolific author with many titles to her name. She has many books about bunnies for April. These printables for the Runaway Bunny are excellent.
Her other great book is The Important Book. You can use The Important book as a pattern for many writing assignments. This blog post by Kindergarten Nanna has several printables that you can use to help your child with writing using The Important Book as a template. I thought they were very helpful.
Lastly I have set up a Pinterest board with some ideas on using Margaret Wise Brown books. She is truly a classic author.