On a conference call with analysts, Barnes & Noble CEO Steve Riggio said its Nook ebook reader is the “single best selling product” in the company’s portfolio. He also said, thanks to the Nook, the company has seen an uptick in traffic to its retail and online stores.

The Nook helped the company boost its online sales by 67%, which could’ve been higher if the company had more units to sell in its inventory. He declined to breakdown unit sales figures for strategic reasons, similar to Amazon, but he said having Nook in its portfolio is critical to its strategy going forward.