The Pragmatic Programmer: From Journeyman to Master
I was introduced to this book several years ago by some Thoughtworkers I had the luck to be working with. After a bit of a dip in my passion for writing software this book really brought back my interest in being professional about writing great stuff.
I was chuffed when the Geek Book Club I started a few months ago decided on it as the first book we should read as a group. It was a second reading for me and I can say that it's just as good second time around. The book is full of sensible explanations of practical tips. Many of them are things that we all know we should do, but somehow don't like "The Cat Ate My Source Code". But other aspects challenge our thinking about some stuff more deeply; like the discussion that ensued around Domain Specific Languages and their good (and bad) uses that our group had while reading Chapter 2.
So much of this book is the foundation of individual agile practices (if there are such things) that it makes sense for everyone to read it. Interestingly it's also on Joel Spolsky's Software Management Reading List which is aimed at those wishing to manage software development rather than those wishing to do software development.