Despite not strictly being a managerial book, they also mention a couple of insights that I thought would be helpful for any manager. The point that most stories are learned in pieces resonated with me - you get the gist from an email, pull in a couple more details from a conversation, and overhear a bit of gossip in a meeting. This means that a well-informed manager is reflective of someone who is constantly gathering information. They also add that the time to switch from collecting information to asking questions is when the time is right to act on the answer. I liked the reminder that the best type of question focuses on the specific - rather than asking "how can we do better?", ask "how can we help you do X?"
To put it another way, a good manager finds ways to collect information and acts on it at the appropriate time. This is best accomplished with a proactive approach. The worst idea of all is to remind the team that "the door is always open", implying that its the team's responsibility to share information. The intention is good, but it's rare for employees to storm into the manager's office with a long list of new issues. (This restraint could be for completely plausible reasons, such as being too busy with the work to take advantage of the open door policy.) This will limit the scope of collected information to whatever the team sees as relevant, which neglects any perspective unique to the manager. If the door is open, then walk through it and take the initiative with the team!