Children’s books were different back then.
It's a super long book of hymns. I'm not sure how many of them are popular nowadays, but it does include some notable ones like "Onward Christian Soldiers," "Rock of Ages," and "Holy Holy Holy". There's a bunch of like stories about the person or people who wrote the hymn, and why it was written. Each hymn is accompanied by an illustration of cherubic children or angels singing, or something like the Virgin Mary or just generic birds.
It includes the actual scores to all of these, with words. For a child to like this book, they'd have to be very interested in the history of hymns. It's mildly interesting from a historical standpoint, but probably not to children of today.