Recommendations for directs?

Hi MT group, 

I supervise a small team of service technicians and have two who are looking towards their next step in the technciain ladder and possibly into management at a later date. I want to expose my star guys to good content that broaden their horizons. 

I am currently listening to: Upstream - The quest to sovle problems before they happen at the suggestion of someone in this forum. So far I am enjoying the book, as it encourages the reader to look beyond the problem. If this oppinion continues I will most likely recommend my all-star technicians read this to start on a succession plan. 

Other books/authors I'd likely recommend depending on the direct:

Developing the Leader Within You -  Maxwell

The Effective Manager & Hiring Manager - Horstman

Thinking, Fast and Slow - Kahneman

The Personal MBA - Kaufman - Recommended by jrb3

Turn the Ship Around! - Marquet

Start With Why - Simon Sinek

What are some other good books you would recommend to your directs?

Thanks!