What business book (and lesson from it) are you implementing?

I'm reading Good to Great by Jim Collins. One truth (which may seem obvious to you) is the high correlation between successful/great companies and their leadership. But not just any leadership. Level 5 leadership. Level 5 leadership is a paradox in itself. It represents a hybrid of humility and unyielding determination. These leaders are ambitious, but their ambition is primarily for the great goal, the organization and its purpose, not themselves. Our leaders are now more aware of giving praise to their teams (it must be genuine), rather than claiming success as their own. Do you have a book and lesson that you can share?