Planet of Judgment
I liked the fact that name SF writers were taking on Trek novels, back then.... but honestly.... reading 'em today... they just weren't that good. Probably my fave of that era is "The Galactic Whirlpool", but since it was Gerrold he already had a leg up on what makes good Trek.
was pretty strong too. It's clear that Joe Haldeman knew his Trek, or at least researched it well, but he also brought his own sensibilities to it in an interesting way, particularly using his military experience to flesh out landing party procedures.