I was doing some heavy-duty numerical programming at my last job, so my boss bought me Numerical Recipes in C as a reference. Most of the time I didn't need to use any of the code from the book; I was mostly converting some existing MATLAB code to C. The Numerical Recipes book just kinda sat on my desk, every once in a while I would crack it open and read about a random subject. The chapter about pseudo-random number generators was pretty interesting, but I never really looked to far into the actual code. See, each subject has a few pages of high level explanation followed by a few printed C programs. The explanations were interesting and pretty easy to understand. As I wold find out though, the code was a complete mess.
After I spent about an entire work day working through every line of the code, scrapping it and starting over, going through it again and still getting the same memory error, my boss decided to write me a new interpolator in MATLAB himself. I still have no idea what was causing the error. I could have translated the code incorrectly, it could be that I was running the code with a different compiler on a different system, or it could just be a typo in the book. The only thing I know for sure is that if I never see their code again it will be too soon. Anyway, once I got the code from my boss, I translated it into C and got it running in the program in about 45 minutes.
With professional programmers and professional mathematicians ruled out, the only possible audience left for this book is non-professionals; reducing the status of this book from tool to toy. Like the swiss army saw before it, it's a toy dressed up as a tool. Moreover, it's a toy that you should, under no circumstances, use as a toy.