It reinforces just how revolutionary the discovery of the concept of zero was - a lot of cultures had groped toward a place value notation system, ie writing 429 instead of (400) (20). (9), but this falls down when you try and write 409 unless you have something signifyng nothing. It is pretty clear that our use of it stems from Indian mathematicians of around 800 AD.
A lot of the book is simply well-illustrated cataloguing, but there were a few other points of analysis that jumped out at me. Ifrah lays out several proposed explanations for the origin of Roman numerals, before coming down with an interpretation where they came from notches on tally sticks. His description of the destruction of Mayan civilisation is intriguing and awful - is it really true that only three Mayan manuscripts survived the Spanish conquest? And of course I was interested to see how the medieval numbers that I was once familiar with fit into the longer tradition of the Hindu-Arabic numerals.