+1 on Talent Code. Not a golf book, but I'd struggle to imagine anything that you could read that would be more important ('tho BBax makes a good case for the rules, assuming a US audience

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Even less golf-specific than the Talent Code, but a tremendous book for anyone who is going to be mentoring young and ambitious talent, is Practicing by Glenn Kurtz. Should be on the reading list of anyone who thinks they might be driven to try and achieve anything.
For golf books, I'd be tempted to recommend Pelz Short Game Bible, Stan Utley (either Short Game or Putting) and Percy Boomer. Not for the golf information per se, but for the exemplification of three very different approaches to teaching.