I wish I’d had this book when I first started out as a programmer!
It does not cover debugging techniques e.g. debuggers like pdb but instead focuses on a general purpose debugging methodology that could be as easily applied to many disciplines not just software development. Its very short and very focused on the topic at hand with no fluff and some very amusing war stories from the debugging trenches.
This book is useful to anyone who needs to figure out why something is not working and resolve the issue. I own both the paper and electronic kindle edition so I can have it at hand at all times as a reference.