I know some readers find the plots far-fetched, but I don't think there's anything in there more outlandish than TOS. IIRC, in one novel some admirals express the opinion that Calhoun's adventures can't be real, and when its pointed out that Kirk reported far wilder things, they say they think Kirk falsified his reports as well.
In his preface to the Star Trek: The Motion Picture
novelization, Gene Roddenberry employed the conceit that Star Trek
had been a 23rd-century dramatization of the real adventures of Kirk and his crew, and said that Kirk had criticized it for its inaccuracies and exaggerations.