If you're a fan of Star Trek - particularly the Original Series - I can't recommend enough Harlan Ellison's 1996 book about The City On The Edge Of Forever. It's arguably the most famous episode in the series.
No, make that infamous - City had a bruising trip from page to screen. The TV episode is justly acclaimed as one of Trek's finest - if not the finest - hours. It's the one that has Kirk and Spock literally leaping into the past to stop a drug-crazed McCoy from dramatically changing the future. The show won the Hugo Award for Best Dramatic Presentation and is a classic episode.
But it could have been even better.
Harlan Ellison's book contains his original script, which won him the Writer's Guild of America award for Best Teleplay. There are significant differences between what he originally wrote and what ended up on the screen. In the book, Ellison sets out his side of the story in a remarkable 80 page essay. It's an abject demonstration of how Hollywood treats its writers. Ellison spells out how his script was dumbed down and diluted on its way to production. Show chief Gene Roddenberry is repeatedly shown making out to the media that Ellison was the bad guy. William Shatner, God bless him, doesn't come out of it well either. If there's one lesson to be learned, it's that you do not cross Harlan Ellison and get away with it; his pen is mightier than your sword. It's fascinating stuff, written more out of frustration than rancor by Ellison. After nearly 30 years of bottling it up, the book was clearly a long overdue catharsis.
Now the really good news. There's currently a Kickstarter campaign to fund an audiobook version of Ellison's book. Not only will there be a full cast reading of the original teleplay (including LeVar Burton, Robert Forster and Jean Smart) but that epic essay will be read by Ellison himself. Plus there's a raft of extras.
As I said - if you're a fan of Star Trek or Harlan Ellison or both - this is an investment well worth making.