By my HBS mentor (and fairy godmother) Linda Hill along with Greg Brandeau, Emily Truelove and Kent Lineback outlines the leadership needs of the future.
Draws on nearly one hundred interviews with highly creative people. I find it an invaluable coaching resource as it reminds me how many different ways there are to achieve enduring creative success (Note: I have not read the newest edition).
I rarely refer to anything but pages 84-91, where the great Russian psychologist outlines his theory for the zone of proximal development...although all of Vygotsky's amazing work was groundbreaking.
I discovered this book by the famous MIT social scientist and consultant in grad school, and it forever changed how I work. He shows how engineers, architects, managers, psychotherapists and town planners really go about solving problems. Not the easiest read, but fascinating nevertheless.