Strengths: Excellent selection of topics, with good references and enough discussion of the underlying scientific theory. Thoughtful and well-written. DO NOT USE MERELY AS A COOKBOOK!
Weaknesses: Antiquated code, basically FORTRAN with a C veneer. Although the code works as is and is blazingly fast, it's not usable as a basis for further code development -- readers will want to recast the ideas and algorithms in their own up-to-date C code. For example, his arrays start at 1; the only data structure is the array (ugh!), there are no structures. Things get hard to understand when he starts packing multiple array indices into a single composite index, then unpacks it (see, e.g., the code on autocorrelation functions, Chap. 5).
However, the awkward code is a blessing in disguise -- write your own and you'll learn an incredible amount! This book gives you all the conceptual tools to do this, and you can use the code supplied (available from the publisher) as a benchmark and check. Actually, there are a few bugs in the code, but considering its complexity (much of which is unavoidable), it is remarkably reliable. In general, the code is optimized for efficiency, not for ease of maintenance or generalization.
The author deserves any amount of thanks for writing this unique and indispensable book, which is clearly the fruit of many years of practical computing experience in a 70's, early 80's UNIX environment. The code has not aged well, but the ideas it embodies are timeless.