How many world class instructors can chime in on one post? - I'm in the company of greatness!
My personal offerings to the list:
Tommy Armour - how to play your best golf all of the time - great historical background, (lots of discussion of lag, pp#3, etc.).
Bobby Jones - rights and wrongs of golf - again "lest we forget from whence we came".
Nicklaus - Golf My Way (go ahead rip me on this one), nice discussion of the effects of the upright spectrum of swing plane to directional control, great emphasis on #3 essential and LOC.
Langer on Putting - Unless you've read it - don't even try to touch me on this one. As thorough as the man himself - end of story.
Nothing is useless unless it purports itself to be infallible. (anyone seen Mr. Kuykendall lately, ahem?)