Numerical Recipes, particularly the
code in it, has something of a mixed
reputation.
Numerical methods are very hard for a layman such as myself to assess: Are they fast? Are they
stable?
Many specialists think they're not. One example is the page Why not use Numerical Recipes? on (sorry, I know you don't like URLs on E2) http://math.jpl.nasa.gov/nr/. I've also heard doubts expressed by a numerical analyst. Frankly, not being an expert on the subject, I'm not sure.
They do do a good job of explaining the bare facts of each type of problem. Certainly (in my experience) enough to give you the vocabulary you need to seek out more specific help. But you'll probably want to consult a numerical analyst regarding the specifics of your problem before using their codes; other codes are often also available, e.g. at Netlib.