Blurring of content/ads, and magazines/books

What does it say when the latest issues of fashion mags are over 70% ads, and hundreds of pages long? It tells me that ads are legitimate content that readers are willing to pay for. It also tells me that number of pages is not what distinguishes a magazine from a book. The author below even makes an offhand reference to these mags as "fashion books"!

Advertising Age - MediaWorks - It's Another Sweet September for Fashion Mags [Emphasis mine]:

The September Vogue shot up like the champion should, clocking 727 ad pages for a gain of more than 100 -- helped only a bit by this year's CondeNast-wide Fashion Rocks insert, which is 15% thicker than last year's. The number of ad pages ranges, depending on the title, from 75 to 100.

Not surprisingly, given the spending strength in the accessories category this past year, the other fashion books were fat as well. W, Vogue's sibling at CondeNast, racked up 477 ad pages, improving over last September by 85 pages. Elle, part of Hachette Filipacchi Media U.S., nabbed 398 ad pages for September, up 27 from last September, according to the Media Industry Newsletter. Time Inc.'s In Style matched Elle at 398, a gain of 33 pages. Harper's Bazaar from Hearst is running 360 ad pages in its September tome -- the largest issue the title's ever published -- for a gain of about 48 pages. And Glamour, though not as strict a fashion play as the others, has 285 ad pages in September, up 10.

These are numbers for fall issues that are not necessarily representative of the rest of the year. But one still might ask, is any editorial content required in these magazines? My instinct tells me that nobody would buy these mags if they were 100% ads, yet it is clear that 85% is ok. What is the curious power of 15% editorial content that turns a catalog one expects for free into a magazine that one would pay for?