We've already had a pretty clear indication that the Barnes & Noble Nook would be going on sale at Best Buy soon, and we now have our firmest evidence yet courtesy of a tipster who has found Nooks aplenty lurking behind the scenes at the retailer. What's more, as you can see in the shot of an inventory screen after the break, it seems all but certain that the launch date is indeed April 18th, although there's still no confirmation of a price -- we wouldn't be counting on any discounts over Barnes & Noble itself, though.