Lt. Zanne wrote:
I understand Chris Chapel's main purpose on TOS was her crush on Spock, but are there any good novels about this character beyond this one aspect?
Certainly! She appears in several great scenes in the ST III novelization, even though Chapel did not appear in the film.
Other interesting Chapel stories include "Night Whispers" (with Will Decker) in "Enterprise Logs", the rarely-mentioned novel "The Trellisane Confrontation" (Chapel's on the cover!), and "The Errand of Vengeance" trilogy, a "lower decks" treatment of events paralleling "Balance of Terror" and "What Are Little Girls Made Of?"
Don't forget that she becomes Captain Sulu's CMO in the "Excelsior" novels.