Barbara Cartland's stuff is commercial. Clive Cussler's fiction is commercial. Grishom's work is commercial. Commercial doesn't mean bad or good, it just means that it's brain-candy...fun...entertaining. Contemporary works like The Bee-Keepers, Bridges of Madison County, or older stuff like Hemingway, LotR, Steinway, Twain are less commercial, though commercially successful, and more lasting. In a hundred years, Cussler and Grishom's stuff won't be being read as much as some of today's less monetarily successful works. That said, and I haven't named good examples cuz I really am rather braindead on my meds -- hazed brain syndrome, you know -- there are commercial works, even commercially successful ones that are going to prove lasting. Hunt for Red October, Silence of the Lambs, Greg Bear's Eon, Dune...to name a few I can think of.
It isn't limited appeal. It's an almost intangible quality that makes the story last. I'm not a writer. I'm not sure what the elements are that make one different than another, but I do know as a reader and as someone who used to run a book store, that certain books stick, no matter how old they get or how outdated. Sherlock Homes stories are a good example.
I happen to be a Cussler reader. I like the brain-candy he provides in his romping stories. I'll skip the boring stuff he dumps in -- his political commentaries and stuff, I see right through his propagandinzing...author whatever you people call it, but the fun is just fun. I may read two a year, though, when I am in one of my stagnations as I call it and need a brain break. Recently, I read the Da Vinci Code, and it really didn't hold me. I skimmed it finally, then trotted to the end to find out what happened...and what happened was dry and unfulfilling to me as a reader. For me, the whole book is nothing more than a series of puzzles with history mixed fact and fable stirred in, and not very well. The answers were completely visible to me before the characters came up with them. It just wasn't satisfying, yet it stormed the best sellers list. Anyway, I think I lost tac.
Later.