Part of what makes Star Trek a TV-centric franchise is the episodic format. Traditionally, Trek doesn't do huge serials, so I would picture it more as one of those series of short stories/novellas rather than one book.
As I mentioned, there have been many ongoing series based on one-shot stories like movies or novels. You just continue the characters and the premise beyond the events of the novel/movie and invent new stories for them. For instance, if it's something like
The Night Stalker (a TV movie adapted from a yet-unpublished novel), in which the protagonist is a reporter investigating a supernatural crime spree, then the subsequent series (in this case
Kolchak: The Night Stalker) would just have the reporter investigate a different supernatural crime each week.
A couple of older examples of novels being turned into movies that then spawned ongoing TV series were the crime drama
Naked City and the long-running soap opera
Peyton Place.
Bat Masterson and
The Untouchables were based on the nonfiction biographies of real people (although the latter biography was largely fiction passed off as fact), inventing new weekly adventures for them beyond the events of the books. (The book version of
The Untouchables was adapted as an installment of the
Desilu Playhouse anthology, ending with Al Capone's arrest, so the subsequent TV series had to make up new, entirely fictionalized cases for the team.)
The modern approach of treating an entire season as a single "novel for television" didn't exist back then. They had serials such as soap operas and children's adventure shows, but they were open-ended, or had multiple brief arcs within a season -- for instance, Disney's
Zorro had three 13-episode arcs in its first season, emulating the Republic movie serials, and multiple 3- to 4-episode arcs in its second season. For that matter, Zorro originated in a novel and a subsequent series of stories, but the TV series didn't directly adapt any of them, just created new stories around the characters and general premise.