The title tagline actually describes the book - Dan Koeppel talks about his first his father's life and how it intertwines more and more with the world of top-level bird watching (Listing), then he talks about his own life and how his father's birding affected him and his family as a whole. I appreciated that he wrote in the things that weren't great - about his family and his own choices, instead of making everyone seem 'okay'. Using the word obsession should indicate something that has sweeping effects, and if the effects hadn't been discussed, the birding would have seemed less urgent, not so much an obsession.
I was pleasantly surprised by the amount of nature still in NYC in the early parts of the book. (I'm not focusing on the fact that a lot of it is gone.) I want to google image many of the birds mentioned in the book, and thought perhaps the only way the book could have beena little better (to me) was if it included some color illustrations of the birds that make important appearances. (perhaps a set of color plates in the middle of the book).