The nicest math book I own
math-blog.com
math-blog.com
http://www.dpmms.cam.ac.uk/~wtg10/mathsindex.html
and the newer stuff is on his blog:
If it's truly a good book, I don't mind buying an updated 2nd edition.
Lots of good book recommendations below, folks. Keep scrolling.
Which reminds me, we should consider the semantics of starting a science/math/etc book club dedicated to important books and concepts.
The Russian school put out some pretty massive volumes, like
http://www.amazon.com/Mathematics-Its-Content-Methods-Meanin...
but I found those to be a little too caught up in the proposition/proof cycle to be useful as a guide to the uninitiated.
That being said, if I wanted to slowly build up a mathematical foundation (maybe half hour a day), would buying a book like this be right place to start? Or should I be looking elsewhere?
If you want to actually be able to solve problems using math (the fun part, for most amateur mathematicians), a textbook would be a better bet. If you stopped math at business calculus and want a great introduction to the calculus that mathematicians use, I wholeheartedly recommend Michael Spivak's Calculus as a next step.
Here is a link to links to multiple reviews of A New Kind of Science. Some of the reviews are by quite eminent mathematicians.
One oddity: I keep looking for a mention of Paul Erdos in the book, and haven't found one.
http://en.wikipedia.org/wiki/Erdos_number
http://www.nationmaster.com/encyclopedia/William-Timothy-Gow...
Thanks to Gowers et al for this fabulous book!