James Blish wrote a lot for Bantam's Star Trek books, including most of the 12 collections that covered each episode of the original series. His stories went into more depth than the episode, but usually not in the direction of the character. This book, one of the first original tales published, fits that mold quite well.

McCoy doesn't like the transporter, Scotty loves to talk about the technology, and Kirk must agonize over the decisions. In this case, the decision is which Spock must die, after the first officer is duplicated in a transporter incident. The rest of the story is original, from a space battle scene with multiple Klingon corvettes to a wild conclusion on the Organian homeworld. In addition to a good story, it was a very quick read.

Later tales, including more James Blish and some of the Pocket Books stories, go into more depth and challenge for the main characters. This book is not great but not bad - right in the middle of the spectrum.