Tony Kern is the best!
I can suggest Redifining Airmanship, is a complete review of what Airmanship is, with so many case studies...even Flight Discipline is good but the first one is much more exhaustive, i bought even "Commander and Crew" P.Denucci but, in my opinion, is too short and dispersive...
Even some author writing about PNL is interesting, like "Coaching and Leadership" A.Deering, is very technical and specific....
Good Luck for your career!!