Recent Rakuten acquisition Kobo reports a ten-fold increase in its number of e-book customers relative to the pre-holiday period. While Kobo hasn't released sales numbers, it says that it has had "hundreds of thousands" of new device activations each day since Christmas Eve, while rival Amazon is claiming over four million Kindles sold through December. Not to be left out, Barnes & Noble says that Nook unit sales (i.e., devices, not e-books) were 70 percent higher than last holiday season — culminating in the company selling "virtually its entire inventory of NookColor and E Ink devices" during the holidays.

Kobo's one of a small group of players with its own content store, and it seems this ecosystem is allowing it to keep pace with established players Amazon and Barnes & Noble, but we'll see if they can maintain it.