Buy the Gunsite TACTICAL PISTOL HANDBOOK
and also THE MODERN TECHNIQUE OF THE PISTOL
by Greg Morrison.
And search on Amazon.com or Alibris for a copy of COOPER ON HANDGUNS
(the 1974 edition is longer and better, the 1979 edition is OK)
If you plan to go to Gunsite in the future, that will get you started. Practice the pistol drills in the Tactical Pistol Handbook in preparation.