I knew I'd be interested in the topic, but not "this" interested. 33 years ago my professional report (LBJ lingo for master's thesis) was on the American vice president, with a preceding paper on the "accidental presidencies."
Admittedly I focused on the 20th century accidental presidents, but even so, Cohen's book brimmed with things that I did not know. I knew nothing about the very interesting presidential accessions in the 19th century, and given that they occurred approximately 20 years apart for 120 years it was interesting to see how the same figures actually played a part in more than one transition.
Terrific book on the White House in the 19th century, and on the many stories surrounding the 20th century presidential deaths and offices well. I learned a lot about the Harding to Coolidge transition that I did not know, as well as some excellent commentary on what Lyndon Johnson didn't do right in the author's view. But, again, the best part of the book was in the highly entertaining accounts of the transitions and personalities in the 19th century. I will never look at John Tyler, Zachary Taylor, James Garfield or Chester Arthur the same again.