As a newly promoted or hired manager, your staff, peers, and upper management will be observing your behavior and results in the workplace. People will want to understand how you operate and what your expectations are. From your staff's perspective, this will range from "How can I please my boss and exceed my objectives?", all the way down to "How little can I get away with?". Your peers will be wondering whether they can rely on you, whether you can be trusted, or whether you will attempt to show them up. Your upper management will likely just have one question in mind:
"Are you going to deliver?"
So, if you are going to make a purposeful change in your behavior and improve your results by reading this book, then the best time to make that change is now. Change is never easier than in the present moment. The longer you delay it, the more reasons or anxiety will develop in your mind that will prevent it from happening. And from your staff's perspective, the more they get used to their new manager's style, the harder it will be for them to accept a change in it. If you don't believe me, try this exercise:
Tell your staff that they can finish half an hour earlier each day, for the same pay.
Three months later, tell them that they have to go back to how it was before.
Consult with HR on how to quickly recruit a replacement team.
Secondly, you have a duty and responsibility as a manager to ensure that your staff hit their targets and also develop professionally along the way. If you don't provide effective feedback, you have no one but yourself to blame if your staff don't perform.
Aside from all of the hard work that you put in to get yourself to this stage in your career, I'll bet there was someone who invested their time, experience, and wisdom in you. Do the right thing and pay it forwards by giving your staff feedback that helps them be the best that they can be in the workplace.