One idea could be to partner with publishers and maybe 10% of the time a user opens a new tab, the book placement is sponsored. Charge based on impressions, cli

One idea could be to partner with publishers and maybe 10% of the time a user opens a new tab, the book placement is sponsored. Charge based on impressions, click-throughs, or by some other arrangement. For users, it keeps the tool free and ideally—if the sponsored placements are good—introduces them to cool new books.