I think there is no one list best for officers or cadets to read.  A lot of it depends on where they are at in their development, their strengths and weaknesses, the area they wish to learn more, etc.  The important thing is to keep learning.  Reading is one way to do that, but there are many others that work well too.  Below are some suggestions for books that may not be on the typical reading lists.  Many of the books others suggested above are awesome.  This is just a few outside the box books.

Leadership and Self-deception

The Innovators Dilemma

What Got You Here Won’t Get You There

Crucial Accountability

Charisma Myth