I've read articles about companies that targeted young adults (13 - 18) with their Facebook campaigns, only to pay for a ton of clicks but no sales because young adults don't have a credit card to make an online purchase. Similarly, I've seen articles that assert that young adults use the library for a lot of their reading material. It's also my understanding that half of the readers who read YA novels are in fact adults. Combined, those assertions would lead me to first target the adults who read YA novels.
When setting up the targeting at Amazon, Facebook and BookBub for a YA novels series, how would you target the ad? How would you successfully reach those readers who can't buy online?