Is it the impeccable draftsmanship and absolute mastery of drawing horses? Is it the scary beasts?
The saucy threats from a wife to her husband? 
Or is it consistently amazing comics coupled with out-of-this-world production? Whatever it is, Prince Valiant Volume 10 1955-1956 by Hal Foster (a past 2012, 2014 Eisner nominee) hit the NY Times Best Seller list. Volume 8 hit the NY Times Best Seller's list this time last year. Volume 10 traverses the lands of Constantinople, Eastern Russia and Camelot in addition to wrapping up stories on the kidnapping of Aleta, Valiant's trusty wife, and hunger problems in Thule.
And we're pretty sure it had to do with this pre-David Bowie yet Bowie-esque look on the cover. Or all of the above.