There is a new book by Susan Crockford called "Polar Bears, Facts and Myths". It is written for children (all ages, actually) and talks about the current state of polar bears. Even though there are constant reports that polar bears are in trouble, the science does not back that up. Polar bears are doing fine.
The book is available at Amazon (I won't link—you'll need to look it up yourself). I purchased the Kindle version for 99 cents (USD). The paperback is $12.99. The book is 44 pages in length.
I must note that those who are sensitive—those who are used to food coming from the supermarket wrapped in cellophane or those who don't eat meat—may find one photo of a polar bear feeding disturbing. Polar bears don't shop in a supermarket, don't "humanely kill" their food and don't cook it before eating. If the reader is likely to be disturbed by this reality, I don't recommend the book for them.
This blog rarely recommends reading of a certain book or article, but I found this particular book quite good. The author has written other books and papers that were quite interesting.
(I am not being compensated for writing this in any way.)