I had not explored Whitman's "Leaves of Grass" before reading this book, and was looking for a portrait of Whitman and his times, not a compilation of "influences," A to Z. In short, I found it dull. The author's writing style doesn't help either, which is straightforward at best, pedantic at worst ("No other biographer has noted...").
If you love Whitman's poetry, by all means buy and read this book. However, if you are looking for a more straightforward biography or a picture of America in the age of Whitman, you might look elswhere. Please, tell me what you find!