Although I'm retired, I've struggled to find interesting work at times during my working life and now that I'm free to do what projects I chose, I've find it hard to know which to prioritise, so I got this book.
I wish it had come out years ago while I was still working. It has a very different approach to other career-guidance books; for instance, it argues for finding ways to try out the jobs you're thinking about - as many as possible - in some form or another, such as work-shadowing because it's only by trying them that you'll find out how much you enjoy them (or don't). Other books recommend doing lots of research first and then making the career switch - thinking first, acting later - whereas he's recommending acting first, thinking later.
He also has some interesting exercises for thinking about how you've ended up with the career you've had so far - that stuff alone was worth buying the book for!
I've found this book a real help in choosing among the unpaid work I've been thinking about and I've recommended it to a friend who has been stuck for years in a job she hates while struggling to come up with an escape plan.
It's short (125pp or so) and I read it in a couple of hours. I like books that say what they have to say without padding it out or repeating themselves to make you think you're getting your money's worth.
Highly recommended. I've just ordered his "The Wonderbox", which also looks great. His website is interesting too - he does a lot of work on how to encourage empathy in society.