So it's really historical fiction, but I don't have a shelf for that yet...
This biography does what much similar fiction does, which is to psychologize the structure of facts. Weatherford does have a very interesting stylized way of writing in three voices: a narrator, Harriet, and God. There is a clear shift in the rhythm of the voices when they shift, which helps with the imagining. Readers' Theater anyone?
Nelson's illustrations are phenomenal. The double near the end where Tubman is leading a group of people and hushing them is one of the most gripping compositions I've seen in a children's book. Nelson's use of the cinematic shots is again clear: the mid range shot is most prevalent throughout the book, with only a couple of the impressive wide shots and extreme close-ups. The cinematic sense of storyboarding is clearly a strength of Nelson's.
This book makes no bones about being a myth-making book, and it wears its religion on its sleeve. It's an honest approach, and one that would give a group of readers an opening to talk about religious beliefs as an aspect of social studies.