If for some reason you're jonesin' to read a history of the number zero, I would hie thee away from this book. Read instead Charles Seife's peerless "Zero: The Biography of a Dangerous Idea," a very similar book (published around the same time, too) that is much more interesting and far more competently written.
Kaplan's book, while not atrocious, is nevertheless poorly brought off and demands a much stronger math background to enjoy -- despite what the blurb on the cover says.
I will admit, though, that, in addition to being a capable mathematician and scholar, Kaplan has organized and researched his tale well. Fatally, however, the guy can't seem to write in a natural, lucid way.
Here's a sample of the kind of opaque, gummy prose you're in store for if you tackle this book [p. 144]:
"Only selective forgetting of the past lets us move on, taking what was once dubious as the most banal of certainties, what was gained through struggle as our birthright. So with zero. The sermons it spoke in place-holding shrank to a letter of our thinking's alphabet, its volumes on solving equations to a sentence in mathematical primers."
And this is quite typical. Trust me: Seife is much more engaging, useful, and memorable. His book is considerably shorter than Kaplan's, however.