I've been thinking this for a long time, but it's been a while since I last ventured into a comic shop to put the thoughts into some semblance of order.
(As I recall I think Stephen L Holland of Page 45 said something similar in an old issue of Comics International, but, having no print copy to refer to and the official website being very sparse indeed I'll just acknowledge that I may merely be repeating Stephen's words and carry on).
The big problem, as I see it now, is that there are simply too many graphic novels being published.
When I first started dealing with Graphic Novels as an employee at Nostalgia and Comics back in the 80s and 90s it was easy to keep on top of stock using nothing more than a piece of paper and a good memory. Last time I did it, nearly two years ago it involved a Diamond Comics Star System over 20 pages long with type so small that it gave me a headache to read it and concentrate on it. It used to be that the essential "in stock" list - that bible list of all of the graphic novels that we should not be without was a few hundred items long. Now I imagine it's in the high thousands if not the tens of thousands.
As the graphic novel became the predominant format for the comic medium everyone slowly realised that in the majority of cases, they wouldn't have to gamble on whether to get it as a comic or hope that it might get collected. Generally if it's a major series from a comic publisher (Marvel, DC, Dark Horse, Image et al) it will be collected. And if it's from a literary publisher (Top Shelf, D&Q, Fantagraphics etc) then the graphic novel will almost be their preferred means of publication nowadays.
The problem now is that everything seems to be collected. EVERYTHING.
And this removal of even the most rudimentary sales or quality threshold has the potential to cause a catastrophic industry effect. Because it doesn't take much imagining to transform this graphic novel glut into a very similar situation from the 80s - the black and white glut. Following the success of the Teenage Mutant Ninja Turtles the market was flooded with black and white comics of all kinds. And retailers, completely overwhelmed by the selection and not wanting to lose sales, overordered on the majority of titles. These comics sat in stockrooms and scked working capiatl out of comic shops, many of whom went out of business through a cash flow crisi when it became pretty obvious that the next tutles wasn't going to be happening.
The majority of retailers are in a similar position now with graphic novels.
There's just too many of them. Far too many of them. It doesn't make sense to try to order them all. Financial suicide coupled with a physical inability to rack them.
The only answer has to be going back to a principle all sensible retailers started to use a decade ago when the back issue market practically disappeared from comic shops. The smart retailers realised that there was very little point keeping huge back issue sections that realised almost no money and started ordering comics to sell out in the month of release. If it was a great series with a lot of second month sales or something the retailer was passionate about then it was worth ordering to sell out over the course of a few months. In rare circumstances the comic might actually have a very long shelf life but this was incredibly rare (Acme Novelty Library, Tomine, Lenore etc).
Generally a safer bet for the retailer was to sell out in the first 2-3 weeks. The smart thinking says that any lost sales in weeks 4+ are not worth the risks associated with over-ordering.
I can see a time where intelligent retailers have to decision to divide their graphic novel ordering into two very distinct groups.
The first is the traditional graphic novel. The perennial seller. A book that will be selling from your shelves over and over down the years. Think Maus, Palestine, Sandman, Preacher, Mouse Guard, Watchmen, Love & Rockets.
The second group is those graphic novels that you treat as comics. You only order enough to sell through in the first few weeks. Essentially you're deciding which ones you're going to treat just like a throwaway, transitory thing. I'm sure you can all think of examples in this class.
I'm guessing that many stores are already doing something similar with Manga books. Of course, the serialised format of these books makes it a lot easier to rationalise this. Manga volumes are essentially comics anyway goes the thinking. Therefore we can treat them as comics and not do regular restocks. It's a lazy way of thinking perhaps, but I'm sure it happens all over.
Of course, another option available to everyone is just to not order a large proportion of the books. That works just as well. But how many retailers would have the guts to try that one.
One thing I know for certain is that retailers who don't decide to do something about the problem, retailers who just go on ordering a little of everything published without a definite strategy for ordering are just going to find things getting tighter and tighter.