McCoy gave Kirk the reading glasses in Star Trek II: The Wrath of Khan as a birthday present. TWOK is clearly before the E-A shows up (Kirk even had the glasses in 1986 San Francisco, minus the lenses, before he got command of the A).
Uhh, yes, that is of course the whole point -- that if Kirk needs glasses in the novel, it must be after
TWOK. But it also has Kirk at captain's rank and has him, Spock, and the rest of the crew aboard the Enterprise
, and the only way that can happen after TWOK is if it's also
Well, there is the fact that anybody who commands a starship is referred to as "captain," regardless of their actual rank.