Barbara Cohen (1932-1992) was the author of several acclaimed picture books and novels for young readers, including The Carp in the Bathtub, Yussel's Prayer: A Yom Kippur Story, Thank You, Jackie Robinson, and King of the Seventh Grade.
Certainly very religious, but also a touching, sweet story. Might work better as a lesson for conservative Jewish children than an educational book for others.
My favorite thing about this story was the clear moral at the end. The illustrations were black and white which made the reader focus on the text more than the pictures. The theme of innocence and purity in this story could be applied to many situations and stories.
I use this book every year, originally for second graders, but now first grade. It's a traditional story, and it's got a lesson that applies all year to any service, not just Yom Kippur.