It was because of the original 1966-69 Star Trek series that I first got into (and took seriously) science fiction literature. Finding a good science fiction series on television at that time in the sixties meant you had a choice of various anthology series (The Twilight Zone, Thriller, The Outer Limits), shows with sf-inspired trappings (The Man From U.N.C.L.E., The Avengers) or just plain goofy "monster-on-the-loose" programs (Irwin Allen's Voyage to the Bottom of the Sea, Lost in Space). Yet for whatever it's faults, Star Trek took a much more sober-minded approach to the genre than previous TV shows had.
For one thing, at least in the first two seasons, creator/producer Gene Roddenberry made it a point to hire actual sf (and fantasy/horror) writers for the show, such as Robert Bloch, Harlan Ellison, David Gerrold (his first sale!), George Clayton Johnson, Richard Matheson, Jerry Sohl and Norman Spinrad. (He also considered, then rejected, a story idea by Philip Jose Farmer.) It was because of the shows written by these authors (and often rewritten by Roddenberry and his showrunners) that I started checking out their literary works. Roddenberry also focused on various social and political themes that were at the forefront of the period, such as the Civil Rights and anti-war movements, albeit sneaking them in via various alien civilizations that the crew of Trek's USS Enterprise would encounter.
And of course, there were the characters that made up the crew of the Enterprise: Stoic (if a bit of a skirt-chaser) Captain Kirk (William Shatner), his First Officer, the conflicted half-human, half alien Mr. Spock (Leonard Nimoy), and cranky (and slightly racist) Dr. McCoy (DeForest Kelley) were basically an intergalactic "Three Musketeers" who, along with the rest of crew (including James Doohan's fussy engineer character Scotty), found something to get them into trouble each week. Yet these characters stood out with their own particular charisma and presence, which, despite being ridiculed all these years later (and yes, Shatner often overdoes the dramatics), still has a kind of integrity not found in more recent series. (You have to admit, the Enterprise crew does stand out in a crowd.)
Anyway, with the upcoming new movie "reboot" of the show premiering this May, fans of the original show may be interested in knowing that the original series is now available to watch online at CBS.com. Downloading the shows does require some patience (and there are commercials) but the chance to see these restored shows (now remastered with High-Definition sound and picture) will be worth it. Go here to download.
Related Links: Star Trek materials available at Greenwich Library (including Allan Asherman's Star Trek Compendium pictured at the top of this post); TrekToday; and the book you can find the story Philip Jose Farmer wrote based on his rejected Trek outline, "The Shadow of Space".