Best-seller lists are tricky things, because no one except the people who put them together knows what the numbers really are. Now Publishers Weekly is ripping off the veil and will publish the top 25 listings in the weekly BookScan sales charts with actual numbers attached. Heidi MacDonald explains what's going on at The Beat; this week's chart is free, but after that PW will put it behind a paywall.

This information is fascinating but comes with a couple of caveats. BookScan, which is a service provided by A.C. Nielsen, tracks books sold in bookstores, including Amazon but not including the direct market, mass-market stores such as Wal-Mart, book fairs, or sales to libraries. So when you look at the list, it's useful to keep in mind that some books will do better in comics shops than bookstores, while for others, such as manga and graphic-novel memoirs, the opposite will be true. What's more, BookScan doesn't cover the whole market— Heidi says it captures 80 percent, but her commenters dispute that. In other words, the charts only give a piece of the picture, and it's more accurate for some books than for others.

To me, the most interesting column is the last one, which shows the number of copies sold this year to date. My rough rule of thumb is that a book has to sell about 3,000 copies to break even, and by that measure, most of the non-superhero books are doing well (and the superhero ones are probably selling gangbusters in the direct market).

The other interesting thing is that a book can make the chart with a relatively modest number of sales for the week; the No. 25 book in this week's chart is the third volume of Sailor Moon, with 306 copies. This explains some of the head-scratchers that were noted when The New York Times debuted its graphic novel charts. Does Omamori Himari have a huge audience? My guess is no, but it does have a solid fanbase, and as Vol. 7 came out in bookstores two weeks ago, all those fans are buying it at once. That gives it a bump in the weekly-sales column, but the cumulative numbers are never going to be what they are for Sailor Moon or The Walking Dead.

That means the end-of-year charts that Brian Hibbs gets will continue to be the gold standard, but for those who like to watch the scene as it evolves, and who can't afford to subscribe to BookScan, PW's excerpts may make interesting reading.