"If I buy this book and it saves me one hour of time writing tests, writing better tests, debugging tests, or whatever, it will have paid for itself." Only if

"If I buy this book and it saves me one hour of time writing tests, writing better tests, debugging tests, or whatever, it will have paid for itself." Only if you have unlimited potential work for that rate, and are actually billing for contracted work, not by the hour. In most scenarios, you will have paid for the book yourself, spent some time reading it (hopefully billable hours) and there is a real chance increased knowledge actually leads to more work, as you now have a more in depth understanding of the topic. To me it all reads like the typing speed vs productivity essays. Yes, you should not be hindered by hunt and peck style typing interfering with your train of thoughts. But never seen someone who writes actual loc or actual content (not casual e-mail replies) where typing speed drives productivity in any way.