I bought my son the first chess book “Learn Chess Tactics” by John Nunn last Christmas, he like it very much. Then I bought him a second book by John Nunn
“Understanding Chess Move by Move“. Now he seldom read the first book, but he kept reading the latter one every now and then even I tried to introduce him other books.
You might want check them out if your kids began playing chess and liked reading. Before you buy them, first check your local library to see if you can borrow for free. And you may want to make sure they are what you want. The latter book is relatively deeper in analysis but your kid might still like it.