Well, they sell cookies/cake/baked goods, so....
Honestly, the cookies are either a love 'em or hate 'em thing. Personally, I love 'em! They are big and crusted with toppings and just a little doughy inside. For me, they hit (favorite is pistachio!), but not everybody likes that. The cake and coffee drinks are also popular. The real hook though is the theme - the place inside is very cool, in a mystic, macabre kind of way. The little character cards that they throw in and all of the other trappings really enhance their popularity.