Sheds a lot of light on its chosen historical period, and there's a lot there to see. The journalism taking place, especially, was truly fascinating. In fact my biggest complaint with the book might be that she sort of drops the journalism thread following the McClure's shake-up. She does touch base with those characters sporadically throughout the rest of the book, but not with the care and diligence that she employed before. In a sense it's a shame that Goodwin is a presidential historian, because I would have loved for this book to be centered on Ida Tarbell herself.
In any case, it's a beautifully written book; always compelling and informative, as I've come to expect from the author. I have a richer understanding of American history for it, and certainly a clearer understanding of Roosevelt & Taft. Highly recommended.