I enjoyed each of the books enough to recommend to anyone else. Each book focuses on some niche of life and each author does a nice job narrating those.
The Ghost Map is about cholera in 1850's London and gives rise to one of my favorite analogies. The characters are Holmesian in many descriptions. Moonwalking with Einstein follows the familiar pattern of much current popular writing and much of it swung nicely between the author's internal and external experiences. The Devil followed events - many unknown to me - in the Chicago World's fair that foreshadowed many things about both the city and nation at the beginning of the 20th century.
My reading enjoyability is based - subjectively - on pace, readability, formatting, ability to drop in or out, hyperbole (a negative number), the quality of content and multiplying these weighted factors by what percentage of the book would have been enough (almost all books are too long).
My amended Flesch-Kincaid scale is;
<4 - Reader's Digest, 5th-9th grade level
4-7- Your life insurance policy and Time Magazine
>7 Harvard Law Review, University graduates