If I have a friend who I know is interested in a particular author, and I notice that that author has released a new book, is it evil for me to tell my friend?

I don't think it is. I'm connecting a producer and a consumer in both of their best interests. When the producer is the one who asks an entity like Facebook "who enjoys this author?" and advertises the new book to them, why is this evil?

People have desires, and without advertising it is very difficult to connect those people with producers who can fulfill them.

I think advertising isn't inherently evil, just some tactics used to persuade people with misinformation.