One of the key misunderstandings in the legacy publishing industry is that future purchases of product are based on factors as superficial as "color of package" or "size of print on label" would be in another consumer goods industry. Just because someone bought the Twilight books and enjoyed them does not mean that same customer is going to buy something that "looks just like Twilight." And it's a foregone conclusion that if the product packaging and promotions are designed to capture the Twilight audience, whatever audience the secondary product achieves will by its very nature be a smaller audience than the original group.
Which brings me to why? Why? is Nielsen BookScan used for product purchase decisions? It doesn't really bother me to offer business advice to my competitors, especially since I'm relatively certain these competitors, even if they understand what I'm saying, are prohibited by their corporate structures and strictures from taking this advice and putting it into action. Nielsen BookScan isn't used to identify leading and emerging trends and tastes so much as it is to say "yea" or "nay" to single-book or limited-series book purchases from established authors. As the Forbes article I linked to above describes, the service is being used to shove established authors to the curb if their prior sales are "too small." As the article covers, the BookScan numbers, especially from the past, don't capture the entire market, and may be widely divergent from actual sales, depending upon the market segment and sales channels for the book/author in question.
But that's really not the problem. The problem is making purchase decisions based on what somebody else did in the past - bearing NO relationship to what the potential market might be for the work currently on offer. Nielsen BookScan simply measures what is selling and at enterprise-level packages, can provide some in-depth analysis and tracking of what sold in the past. Since just about 0% of what sold in the past was brought to market with actual marketing tied to its development, this is just a record of what worked or didn't in the chaotic marketplace. It doesn't say what "could work."
I'm sure someone out there is working with this data in a creative manner. But using old BookScan data to say "no" to an author's work? Work that may be utterly unrelated to the prior work that didn't perform as well as expected? Work that may not have performed well because it had ZERO connection to any potential market audience and was just slammed down wherever, whenever, however? That's like saying, "Ah, these Oreos. I've never seen them before. I see they sold poorly in Shanghai last year. Next!" Ah, Kraft (Mondelez) has had such adventures with the cookie. By the way, Oreo sales are softening in China due to increased competition and increased awareness of the health issues related to overconsumption of processed snack foods.
Do my legacy competitors really think people bought the Twilight books in such numbers because Edward was a vampire? Really?
I got a square Oreo filled with HFCS-flavored wood shavings for them.