If you haunted the SF sections of mall bookstores in the 1980s, chances are pretty good you'd come across a series of paperback books called The Best of TREK. While they were usually shelved with the official mass markets published by Pocket Books and Bantam, they weren't tie-ins at all, but rather collections of essays published in TREK, a long-running fanzine devoted almost entirely to criticism and analysis of the series. Edited by super-fans Walter Irwin and G.B. Love, TREK was published regularly from 1975 to 1995, and the best essays were collected in paperback editions released from 1978 to 1996, first by Signet, then ROC.
Since TREK was not a house organ of Paramount, and since Irwin and Love were unable (or unwilling) to license the official images of the cast members or the iconic sets and spacecraft for the cover art, they went for the next best thing: Enterprise-ish starships, usually engaged in some sort of insanely badass action, often with a military theme atypical of the original series' peaceful mission (though oddly reminiscent of the space carnage of the Abrams movies). Collectively, these covers tell the story of an alternate Starfleet that never was.
Ironically, though, the space opera theme of the covers frequently belied the contents of the books, which were often cooly academic in tone and unwilling to turn a blind eye to the franchise's faults (particularly the militarization of Starfleet in the '80s movies). If you were a die-hard middle school aged Trekkie (okay, Trekker, whatever) looking for action and adventure, you might be in for a bit of a disappointment when the first "story" turned out to be a rigorous survey of the 1960s Gold Key comics. Or you might have your mind opened up a bit...
Like a lot of fan-oriented publications, TREK was pretty much rendered obsolete by the rise of the Internet in the '90s, and both Irwin and Love died in the early 2000s. But they did get to see Star Trek develop from an obscure cult phenomenon to a huge mainstream success, and numerous fans who went on to write for TNG and the other spinoffs were influenced by the meticulous and insightful articles published in their magazine. If you can track these down, they're pretty danged cool.