Part biography, but mostly a historical retelling, this informational book was well complemented by Gerstein's illustrations. Much like Byrd's illustrations for the Ben Franklin book, the ink drawings have a hint of old engraving to them that makes the book feel in the correct period (interestingly, the palette was almost identical to Byrd's Franklin book).
The 'slice' of history is again a refreshing approach, because it allowed me to see both Muir and Roosevelt in some depth through this one experience. One of the nice details Rosenstock wrote was how Muir was annoyed by Roosevelt's constant stopping to make speeches and talk to reporters. The sources listed at the end give pointers to both some primary and secondary sources. I was disappointed that Rosenstock mentioned her access to the Muir-Roosevelt correspondence, but gave no details on how she got to look at those letters--not even cited in her source list!