I'd also recommend the Level 2-3 "Coaching Certification Manuals" from the Canadian o-federation. These are a bit old (1985 and '90) but much more interesting for athletes than they might sound.
Level 2, ~90pages by Ron Lowry, has good coverage of the usual advanced techniques, training, analysis, etc that appear in other o-books (I have most).
Level 3, ~140pg. by Ted de St Croix (10th at WOC Long 1985), skips all of that and is basically bonus material for national team coaches and athletes, covering stuff like race strategy in different terrain types, optimum speed, terrain running technique, relay racing, fitness testing, training plans, elite training camps, relaxation/concentration/visualization techniques, team selection, and even international travel issues. I haven't seen any other english book with such elite focus.
I think I bought mine from
Gale ten years ago, it looks like he still has them.