It (and the book on which it is based) are amazing. Virtually every older applied mathematician has a copy of the original Abramowitz and Stegun, which was supported by the National Bureau of Standards, prior to NIST. The successor (http://www.cambridge.org/us/academic/subjects/mathematics/ab...) is really an incredible achievement. The reviews are hilarious. One notes "The book is quite heavy; for convenience, one might be inclined to place it on a stand, as with an unabridged dictionary". Another review begins "This is like trying to review the bible".

The online version also lets you get LaTeX for everything, and has many other features. But the print version is a thing of beauty.

In full disclosure, the Editor in Chief and Mathematics Editor, who devoted the last 13 years of his professional life to the project, was my stepfather.