I guess I don't get it. Disturbing trend...? I'm not sure I understand exactly what Monte means by that statement. I see some small semblance of a trend with a few publishers and a faux-book cover style, and I understand what he is saying in the column, but I am not sure why and on what basis he finds it "disturbing" that some are using one style of cover, or variations of it, while others are using other styles of covers. There have been game books as far back as I can remeber (pre-RPG, early to mid-seventies) that have been mocked up to appear as etched leather (or similar styles like "official documents or dossiers"), and its only with the advancements in computer graphics that it has become a bit more prolific. I wouldn't place too much emphasis on the core books having that style as the primary influence, though admittedly some. Sometimes a good idea is just a good idea, regardless of who happens to take it to its natural conclusion slightly earlier than another.
Monte suggests a couple of reasons why some folks are going that route (economics and suggestive-compatiblity), but he seems to suggest that those reasons are less-than-ideal, perhaps even poorly chosen. Given the great number of products on the market, it is certainly not at all an epidemic to use faux-book covers. Is it really a problem for customers to have a wide array of choices that includes that particular style? Would it be better if all publishers were to follow a trend to avoid the use of faux-book covers?
Personally, I prefer covers to have illustrations with a feeling of action about them, although the faux-book look for the core books seems quite appropriate to me since they were encouraging a slew of other publishers to build up the supplemental library, as it were. I think that the choice of the faux-book style for the core books was a wise and judicious choice on the part of WotC marketing as it allows for supplementary publishers' choices to be less likely to clash thematically with the books they are supposedly supporting. With the number of fans that already don't stray beyond the books published by WotC, I can't imagine how much more difficult it would be for fledgling publishers if the the core book covers were riddled with images of those creatures that WotC has deemed off-limits, such as beholders or mindflayers.
Monte's opinion does bear some weight on the grapevine with the player populace, so I suppose his voicing of it might influence some segment of the marketplace to turn their nose up at covers that don't meet with his personal tastes or approval but I sometimes wonder how aware he is of his influence when he writes his columns on his publishing website and, for that matter, when he writes reviews. I guess if Monte's point is too correlate his opinion of acceptable style with player retention and new player recruitment (as he seems to suggest is, or used to be, his goal to promote), then some numbers need to be examined to see if his feelings about the trend are truly an indicator of how that trend is manifesting itself. How many books are on the market that utilize this supposed trend and what are the sales numbers of those that do, versus those that do not? Sales numbers would seem to be the only true indicator of which covers might be drawing in new players or appealing to those already in the fold. If there were identical core books to those on the market also available that had non-faux-book covers (but otherwise the same material within), we might have a real baseline on which to draw some conclusions, but barring that we really can only try to determine if the core book sales were a successful effort...and to further determine if sales goals are being met by other publishers that utilize the faux-book style covers.
Naturally, one could argue (as some here are doing) that the material behind the cover has as much or more to do with those numbers, but that would, of course, be an alternate, personal preference, simply more conjecture, and seemingly no more valid than the opposing argument in actual point of fact without numbers weighted in that direction. At some point, IMO, there is just no getting around the actual numbers and you have to put at least some trust in the them...or, I suppose, do what you can to change the numbers with whatever influence you can bring to bear. I wish I had some, or he had some and shared them to validate his claims.
From my limited perspective, the industry still seems to be healthier than it has ever been in the past, and gamers seem to have a vast array of products (with varying cover styles) from which to choose, so I am not quite sure what it is that has him so "disturbed" that he feels the need to label one style or another as good or bad in his high-profile column. Maybe he'll pop by here and explain his motivation for the column and if he has any numbers to show why others should, perhaps, feel "disturbed" as well. I, for one, need a bit more than what he has given to feel that it justifies labeling other publishers' choices in such a way, and I'll need quite a bit more to get to a "disturbed" level of concern.
Maybe that's just me...