Kobo's calling the Mini "the world's smallest and lightest e-reader" -- a bit of a dubious claim (given the existence of the Txtr Beagle, for one), but it can certainly lay claim to being one of the most compact mainstream devices in the space at 4 x 5.2 x 0.4 inches, compared to 6.4 x 4.5 x 0.39 inches for the Kobo Glo.
ENGADGET: Kobo Mini review: does the world need a smaller e-reader?