Tips for getting readers to read Book Two in the series?

I have a link to buy Book Two AND the first two chapters of Book Two at the end of Book One. Each book in this YA Paranormal Romance series follows a different couple with their own happily-ever-after ending, so the reader isn't going to appreciate a cliffhanger. :(

The female lead of Book Two is best friends with the female lead of Book One, so the reader does have a chance to get to know her, but I'm wondering if that isn't enough? Book One alternates each chapter between the male and female lead POVs . . . Would it be weird/crazy if I added a chapter or two toward the end with Book Two female's POV? I'm wondering if my readers aren't getting as emotionally invested in her as a secondary character.

Do you have any tips/tricks on how to get readers to move from Book One to Book Two? My current read-through rate from Book One to Book to is 44%. I'd like to get that higher ❤️ Thanks in advance!! 😁