The book I have has the teaser and the first act. Plus the original and another draft.
I don't even think Harlan was a bad fit for tv, just not Star Trek. He wrote two Outer Limits episodes, and they were two of the best of the show.
But he still needed Bob Justman to rein in his imagination to make it affordable to shoot. Ellison's "Demon With a Glass Hand" was supposed to be a chase across Los Angeles, and Ellison couldn't give them a draft that would be affordable to shoot, so they were on the verge of scrapping it altogether -- until Justman had the brainstorm to set the entire thing inside the Bradbury Building.
It makes me wonder if the space pirate version of the Enterprise inspired the Mirror Universe.
The original idea behind "Mirror, Mirror" wasn't about an evil Enterprise
at all. Bixby's outline was just about a different version of the Federation with various differences -- Kirk was married, McCoy had a beard, and some technology was more advanced, but they didn't have phasers, and thus they were losing a war to hostile aliens (though Spock himself was more savage). Although it's possible Ellison's script may have influenced the decision to rewrite "Mirror, Mirror" with an evil-twin Enterprise