It’s worth noting that B&N, like all of the stores other than Amazon, is hard to gain traction in via advertising because it doesn’t have a robust and popular affiliate program like Amazon’s. For this reason, advertisers are less willing to send traffic. As of this writing, the only truly reliable way to reach Nook readers and hence gain non-organic traction is via the list advertiser BookBub. If you can get listed on BookBub — something