If you are trying to teach counting backwards, this book will be helpful. I recommend not using this book with younger children who have not mastered their numbers or counting. Older kids will think some of the text is humorous, ex: "Nine little crocodiles trying to lose weight, one of them tried till he dropped, and then there were..." however, other children may see it a bit morbid, at least until the end where all the crocodiles return!
Ten Little Crocodiles is about how want to try something new. Each time a Crocodile does something new, one disappears. The story ends up with only one of them left, and then on the last page, all the crocodiles appear again. Children can do a similar activity regarding the crocodiles to show them how to count to ten in the classroom.