A great looking book called The Universal History of
Computing by Georges
Ifrah.
I have a 3 volume set by the same author on the history of number
systems. Volume one covers the 'ancient' number systems, Volume 2 covers
(mostly decimal) positional systems and Volume 3 covers computing. I
found his history of computing to be 'different' to say the least, but
the books are very interesting none-the-less.
-tony