What is the author's tone in Bonhoeffer: Pastor, Martyr, Prophet, Spy by Eric Metaxas?

The overall tonal quality of the book is, in some ways, difficult to pin down. On the one hand, because it is a biography and because it relies so heavily on reportage of historically documented events, there is definitely a sense of objectivity about much of it - or, at least, of a degree of objectivity. Beneath the surface, however, there is the lingering sense that ultimately, the book is significantly less objective about its subject and its themes than it initially appears.