a very interesting subject. Sacajawea by Anna J Waldo. Historical fiction but she covers all of the known facts. Glimpses of the Lewis and Clark journals and other researchers writings are in there too. There is a question of how long Sacajawea lived and although Anna takes the long life view, she also has all of the facts surrounding the controversy. Lots of good stuff about the Lewis and Clark expedition. Another plus is that it is 1424 pages long!
If you enjoy American history, you'll enjoy this.