Become a Better Leader in 30 Days by Steve Richardson is not a specifically Christian book, but it is written like a devotional. In 30 brief sections (just 1-3 pages each), Richardson gives you a principle to reflect on along with an activity to incorporate that principle into your day.
His thinking on topics such as crisis, vision, delegating, trust, meetings, etc. flows out of years of leadership experience. The approach is unapologetically practical and designed to be applied right now.
Use it like a devotional, reflecting and acting on one of these segments each day. And when you’re done with it, give it to someone else. In fact, this book would be a great gift to give to a non-Christian business person.