As others have said, this is a tricky book to rate.
I've been reading about the Lindbergh kidnapping since the late '70s. This book contained information that I hadn't seen before, which I found interesting. It's bibliography is quite extensive, so that's helpful.
I appreciated that Behn included so many of the players, and he did a good job of introducing them and keeping them sorted out with a minimum of confusion; however, Behn allows his personal opinions about the various "characters" to creep in rather than presenting facts and allowing the reader to formulate their own opinions. There is so much detail that has been added that is just not necessary to the story of the kidnapping. Two examples, delving into the personalities, careers, and detailing the platforms of the two candidates for president in the 1928 and 1932 elections, and all of the trials and tribulations of Gov. Harold Hoffman's political career. There are already so many characters to keep track of that repeated distractions of extraneous information makes that task even more difficult and bogs down the narrative.
I also found distracting Behn's method of referring to the characters. Lindbergh was often referred to by his full name or as "Charles A. Lindbergh" or even worse, "The Lone Eagle". Is his middle name or initial really necessary? Referring to Lindbergh, Jr., as "The Eaglet" drove me to distraction. Most of the other people had nicknames, too, and Behn mentioned it too frequently (Finn Henrik ("Red") Johnsen, William J. ("Wild Bill") Donnally, Paul T. ("Pop") Gebhart), Jack ("Legs") Diamond, Vincent ("Mad Dog") Coll.... ). Even characters who were mentioned in passing had full titles and nicknames included (General John J. ("Black Jack") Pershing, General Henry H. ("Hap") Arnold, Lieutenant Arthur T. ("Buster") Keaten and endless others.) Maddening and distracting.
Including all of the people that got involved in the case gives you a clear sense of the mass confusion that was going on. While I don't believe the author convincingly proved his premise of how the child died, this book gives you a good sense of the odd behavior of Lindbergh and his wife. Lindbergh was given an inordinate amount of control over the investigation, and it seems clear that he knew more than what he was telling. Have things really changed all that much? Reading anything about the JonBenet Ramsey case convinces me the answer is no. People with wealth, fame, and social status are given privileges that they shouldn't have, and the end result is that cases are compromised because of it.
The recounting of Hauptmann's court case and eventual execution leaves me feeling sad and angry at the extent of the manipulation of the "evidence" and the outright lies told to convict him. I never believed that Hauptmann was in any way connected to the actual kidnapping, and this book certainly reinforces that belief.
On the plus side, the author's chronology helps the reader keep track of the many players in the story. On the negative side, lots of extraneous information and a conclusion that is not strongly supported by evidence and is not convincing.