The book follows The Sweethearts of Rhythm during the second world war, in poetry. Each poem's title was the name of a swing tune and the poems were from the viewpoint of the instrument played. The art looked layered and collaged, and I found out in the artist's note at the end that that was how it was done, but it didn't do much for me.
There is a history at the back, including a picture, that actually tells you more about what happened to the girls during that time and more about the history. I think even fourth-graders would probably like that part first and then the poems and art.