TRO fluff, not numbers, along with sourcebooks is what brought me into the game. I'm an RPG person at heart, not a wargamer. In many respects, I could care less about the tabletop game representation. So I'm a sourcebook/storyline person first.
Considering I'm one of the folks that feels the Battletech setting makes so much more sense if you pretend the novels don't exist at all (at least until some of the later Dark Age novels), I'm pretty much okay with saying that I feel the novels don't hold up well at all. They make the setting more dated, more one-dimensional, and they do a strong disservice to a number of integral players on the setting's stage.
Edit: Hanse Davion is probably the prime example of this. Going by the sourcebooks, you have a very nuanced character who exemplifies the shades of grey that make Battletech interesting. A man trying to avoid his brother's mistakes by having exclusionary focus on one opponent, who also wants to avenge his brother's loss. He is intent on forging ahead in his romanticized vision of a rebuilt Star League under Davion guidance, but continues to resort to the wrong options because of his infatuation with a warrior ethos. He returns to war, time and again, finding a justification no matter what. That's a fascinating character. That's somebody I could actually get behind. This is the guy I discovered in Handbook: House Davion, the singular book that made me at least appreciate the faction after a decade of rolling my eyes in distaste at the boring white-hats.
Unfortunately, most of the fan base seems to have fallen in love with the Hanse Davion of the novels. The one who completely sets aside the FedSuns Romantic and Arthurian basis for a hatchet job of a story that uses 80's American jingoism to talk about how evil the Chi-Comms Capellans are. The novels go on to explain in very specific detail how the 4th Succession War is directly the result of Hanse's "horror" over the doppleganger's treatment at Max's hands. Yes, because millions of deaths for two nations is absolutely worth that. I guess they forgot to tell Hanse that doesn't make you a white-hat, and that the AFFS actually does have SpecOps troops to handle something like this.
For similar examples, read the story of the Clan Invasion from sourcebooks alone, particularly from the more recent ones. Without the trite story lines found in the novels, it actually reads as a pretty fascinating story of the results of conflicting philosophies, both arising from a very specific historical event. The sociological viewpoint of seeing how this has played out over a century or three...that's the kind of stuff that needs to have more time in the spotlight. Respectfully to Mr. Knightmare, I couldn't disagree more. The sourcebooks and TROs do a beautiful job of showing the nuanced, shades of grey that make this setting fantastic. The novels simplify and personalize the story arcs overzealously.
Of course, this all probably explains why most of my AU work focuses on the big picture. I tend to think a view from the ground is a wasted opportunity. With a setting this big, the only view I want to see is the view of my players and their interactions in the setting.
Edit 2: On a side note, this is why I'm so happy that Herb finally struck down the strangle hold the novels had on canon status. Novels don't trump anymore. Of course it never made sense in the first place that they were the trump card.