My problem is upon picking a novel up and something is referenced and I have no idea what it refers to. Examples for me was when reading the opening Titan novels when they came out in 2005, they kept referring to the terrible events on Tezwa. Didn't have a clue what it was all about until a finally read A Time to Kill and A Time to Heal last year.
But anything you actually needed to know about Tezwa was explained in the books themselves. You didn't need to know every detail of it to understand its impact in Titan -- all you needed to know was that it was a traumatic event where Riker was held prisoner. It's like "The Cage," the very first Trek episode ever made, which contained references to a prior incident on Rigel VII where several crewmen were injured and others, including Pike's yeoman, were killed. That unseen event was important to the story of "The Cage," but you didn't need to see it in order to follow the story, because the relevant parts were explained. Same with, say, the death of Jack Crusher as alluded to in the TNG pilot, or Tom Paris's stint in the Maquis as described in the VGR pilot.
Another example was the references to Geordi's lost girlfriend in Indistinguishable from Magic.
That was, what, one or two sentences? Just a passing nod that had no real impact on the story. You didn't lose anything by not getting the reference. In David Gerrold's novelization of "Encounter at Farpoint," he had Picard thinking back on a failed romance with a woman named Celeste. We'd never met Celeste, didn't know the specifics, but that didn't matter. All we needed to know about those past events is how they affected the character's current state of mind.
Every story ever written has some references to events in the characters' pasts, and usually they're references to events that were never depicted in any form. So it shouldn't matter whether you read the previous book or not. All that matters is whether its relevance to the current story is clear.
Fair enough, Christopher. Just call it a minor pet peeve of mine. At the end of the day, it made me look up the A Time to... series and Paths of Disharmony among others, so its win-win for all concerned.