I'm more of a 24th century man when it comes to my TrekLit, mainly because of my love for DS9 and because....well, I already know how things turn out for Kirk and company for the most part, while Picard and the rest are still continuing their adventures (though of course there are exceptions, such as Spock and Scotty continuing into the 24th century).
However, I do love TOS (of course!), and was curious as to the period after the end of Season Three and before the Motion Picture. What would you say are the best novels, comics, etc. set in that period?
Some of the Byrne IDW stuff looks good, but I haven't read it.