I can understand why a lot of people enjoyed this: it's reasonably well-written, it's surprisingly ambitious for a 150-page TV tie-in, and it feels well-grounded in the original show. Unfortunately, despite these positives, Joe Haldeman's slipshod, make-it-up-as-you-go plotting results in a story that, short as it is, still comes across as 80% filler.
For example, in the book's opening chapters, we are introduced to a trio of seemingly important new characters who have formed their own middle-aged love triangle. (Later, Dr. McCoy will also throw his hat into the ring, turning it into a love quadrangle.) In addition, we are introduced to Planet Anomaly, which is mysteriously sustained by an artificial, pea-sized black hole that functions as a miniature sun. All of this is fun and interesting, but what does it ultimately lead to? Well, the new characters mostly walk around with nothing to do, before eventually fading out of the story entirely. Their presence never contributes anything meaningful, nor is the romantic quadrangle ever really explored, let alone resolved. The mysterious black hole remains a mystery indefinitely, because it is never referred to again. So, what do these opening chapters accomplish? I would say nothing apart from muddying up the narrative.
Kirk and his away team take a shuttle down to the planet's surface, which they quickly discover is populated with monstrous creatures straight out of an alien version of THE LAND THAT TIME FORGOT. To their dismay, the shuttle's electronics are no longer working, and so they must attempt to set up shelter and live off the land until they can be rescued. For several chapters, the book continues in the vein of Harry Harrison's DEATHWORLD, as the Enterprise crew use their high-tech tools to fashion a rudimentary military encampment for defending against the nightmarish intruders.
Again, all this is fun but ultimately rather pointless. You see, the Enterprise crew then comes into contact with an alien race called the Arvine, who are in possession of incredible telepathic and telekinetic powers. Using these powers, they are able to complete the encampment in a matter of seconds, eliminating the threat of the nightmare creatures for the entire remainder of the novel. In fact, no such creature is ever heard from again. The Arvine's powers are so great that everything the Enterprise crew does for the rest of the story is sort of irrelevant, since they are completely at the Arvine's mercy.
The Arvine begin conducting tests on certain members of the crew--tests that force them to re-live some of their most difficult memories. Interestingly, we get a scene depicting the moment when McCoy's wife and daughter walk out on him for good, freeing him to sign up for service aboard the Enterprise. We also get a bizarre scene in which he is literally stabbed in the back while partying on shore leave. But even more bizarre is the inclusion of a long passage from James Blish's novelization of the episode "Amok Time." This may be the first novel I've ever read that recycles a long scene from another novel written by a completely different author.
Meanwhile, as Spock and McCoy are re-living painful memories, Kirk is magically transported back to the Enterprise, which was in the process of speeding to Starfleet Academy for help. Kirk decides to turn the ship around and go back to Planet Anomaly. He experiences some difficulty along the way, but the Arvine take care of it, and soon everyone is right back where they were several chapters ago. Talk about great plotting!
The Enterprise crew discover that the reason they are being tested is because the Arvine need data on the behavioral responses of unenlightened creatures in order to decide how to deal with the Irapina, a race of beings even MORE powerful then the Arvine and bent on conquering the universe. The plot then devolves into a bunch of literal "mind games," in which Kirk and Spock engage Irapina representatives on a metaphysical plane in hopes of tricking them into believing that humans are too powerful a race to be easily conquered right at this moment. Kirk and Spock accomplish their goal, delaying an Irapina attack on the Federation by anywhere from 100-1,000 years and instead sending them off in the direction of the Romulan Empire.
First of all, these mind battles are really pointless and silly, despite being well-written. Since the winner is whoever has the most confidence (and not who is the most skilled at any particular thing), I'm not sure why we have to go through the rigmarole of imagined naval battles, sword fights, etc. Then there's the problem with the Irapina themselves: They are WAY too big and imminent a threat to simply vanish from Star Trek mythology altogether once this novel is over. Too bad the Borg hadn't been conceived of yet, because having them as the villains would have made a ton more sense.
Like the majority of these 1970's-era "Star Trek Adventures" from Bantam, PLANET OF JUDGMENT feels poorly thought-out, non-canonical to the nth degree, and almost experimental in its narrative execution. There are even a couple sections written in stream-of-consciousness, which feels about as out of place in a STAR TREK novel as you can get. Joe Haldeman is clearly a more gifted and experienced author than many who were writing STAR TREK at this time, so the book at least manages to avoid that fan-fiction vibe we got from dreck like THE PRICE OF THE PHOENIX. But, alas, that isn't enough to make it good.