I thought it was just one book but it's a whole series! It was made by P.L. Travers and is also a film too. The film and book are both amazing and i also recommend watching a film called 'saving mr Banks' Which is about P.L. Travers' sad story. I cried at the end of it! This book is a classic and is about a serious Nannie who can do magical things. Her name is mary Poppins.

here is a picture of the books:

https://www.google.com/imgres?imgurl=https%3A%2F%2Fimages-na.ssl-images-amazon.com%2Fimages%2FI%2F71TEHABHEdL.jpg&imgrefurl=https%3A%2F%2Fwww.amazon.co.uk%2FTravers-Poppins-Complete-Collection-Books%2Fdp%2F9123525037&tbnid=eZBVxp3WLUCdwM&vet=12ahUKEwiSn_KO7NjpAhWJBGMBHaAIArwQMygDegUIARDsAQ..i&docid=QEBMhBIp_ojhZM&w=954&h=1100&q=mary%20poppins.book%20pink&safe=strict&ved=2ahUKEwiSn_KO7NjpAhWJBGMBHaAIArwQMygDegUIARDsAQ