I bought this book several years ago on the recommendation of another teacher. She said she liked it better than Number the Stars by Lois Lowry. I have very fond memories of Number the Stars, having read it several times in my own junior high years; I really can't compare the two, having read The Devil's Arithmetic so much later and knowing so much more about the Holocaust now than I did.
Yolen's story is similar to other YA books I've liked--a frame story in which the protagonist goes back in time (somehow) to experience for themselves the horror of what "it" was like. For as complicated as the Holocaust was, Yolen manages to compress a considerable amount of the horror into these pages meant for readers of 10-12 years of age. I found the experience of the boxcar horrible enough, and it was just a few pages representing four days.
While adult readers may find themselves questioning the timelines and factuality of the events in the story (some parts seemed too sudden) and finding it lacking in the punch of everything that happened in the Holocaust, I think younger readers will be engrossed by the terrible things humans have done to each other--especially if they realize that similar atrocities are still being committed elsewhere in the world. An excellent book to use for teachers of Holocaust history, especially at the 4th, 5th or 6th grade level as an introduction to this particular part of the past.