However, recently I pick up a few Blish adaptations (Star Treks 1, 2, 3 and 4) at the local library, and I have been seriously impressed by his writing.
1. He doesn't retell the scripts.
Many writers (and students writing about literature) do this. They don't summarize the story in their heads and then retell it in the order that makes sense; they start at point A and proceed through points B, C, and D, even if C is a back-flash and should have been dealt with first. This also happens quite often on sites like the Internet Movie Database. Some people know how to summarize the essence of an episode. Some people only know how to tell you what happened in the order they saw it. I've read summaries on IMDB that made an episode sound FAR more convoluted than it actually was.
Blish is a master at providing the essence. He doesn't retell every incident in the episode, only the ones that hold the narrative together.
2. Blish retains (mostly) a single point of view.
In most of the stories I've read, he uses Kirk's point of view. His voice is third-person omniscient, so he can dive into other people's heads if he wants/needs, but he rarely strays too far from Kirk's mind. Consequently, we are spared a lot of "red-shirt" deaths, which is all to the good, frankly.
Out-of-Kirk's-experience events are summarized in tight paragraphs of exposition. This doesn't mean the writing is all exposition. Most of it is dialog between Kirk and others. Impressively, the dialog doesn't have that taken-directly-from-a-script sound ("There is a monster on the planet," Kirk said. "We must go get it," Spock said. "What do you want me to do, sir?" the red-shirt said.). Blish knew how to write dialog himself, so his dialog-from-the-script has a natural feel/flow. (Writing for the camera truly is different from writing for a short story/novel.)
3. Blish knows how to start a story.
To be honest, I like reading his beginnings more than anything else. Here are some samples:
Simon van Gelder came aboard the Enterprise from the Tantalus Penal Colony via transporter, inside a box addressed to the Bureau of Penology in Stockholm--a desperate measure, but not a particularly intelligent one, as was inevitable under the circumstances. ("Dagger of the Mind")Blish deserves his place as the first adapter of Star Trek stories. And for straight action story-telling, he definitely deserves to be read and emulated!
The Enterprise weathered the ion storm somehow, but one man was dead, and damage to the ship was considerable. ("Court Martial")
Two drops of cordrazine can save a man's life. Ten drops of that unpredictable drug will sometimes kill. When a defective hypospray went off in McCoy's hand, a hundred times that amount was pumped into his body in a split second. ("The City on the Edge of Forever")
The star was very old--as old as it is possible for a star to be, a first-generation star, born when the present universe was born . . . It had become a black star . . . The Enterprise, on a rare trip back toward the Sol sector and Earth, hit the black star traveling at warp factor four--sixty-four times the speed of light. ("Tomorrow is Yesterday")