This has been a good Book for my kids right now ages 5 and 3 1/2. We pair it with another book about St Nick that goes into a little more depth and it give us conversation material. I would buy it again!
This is a very simple book that explains that Santa Claus was a real man- a Christan named Nicholas who loved God and loved to give to help others in need. It doesn't go into a lot of detail or historical facts, and wouldn't bring your child to tears over changing your child's idea of Santa. It just adds a little something better and confirms his reality in their minds. I would recommend it for toddlers and preschoolers, but would suggest something more detailed for older children. Google St. Nicholas for more book suggestions, related projects, free coloring sheets, and a wealth of information to share with your children! Pretty fascinating stuff.
I'd also highly recommend the animated video for children of any age, Nicholas: The Boy Who Became Santa. It has become a holiday favorite in our house.
The book does an ok explanation of the real St. Nick...until the end when the little boy looks out the window and sees the bearded Santa of today's culture outside his window. The book leaves kids more confused about St. Nick vs. Santa. I threw the book away.