I was on a train journey to London, so I reread ReWork by Jason Fried and David Heimnemeier Hansson from 37Signals.
37Signals is the company famous for project management tool Basecamp, which was written in Ruby On Rails… which they wrote! Fried previously distilled their learning from creating this site into the book 'Getting Real'. It encouraged much of the idea of Lean startups. This newer book throws more common sense ideas about business that we all know deep down but somehow don't act on.
I don't agree with everything he suggests, but I think of each idea as an Agile tool to be deployed when needed.
I liked it so much that I lent it to a colleague. I also made it a task in the sprint for him to read it.