I'm sorry but I didn't like Harleen, because I was hoping it was a comic focuses on the past of Harleen, who she was before to start to work at the Arkham Asilum and why that past created the premises so that Harleen became Harley, telling the part where Joker seduces Harleen, transforming her in Harley Queen, in the last chapter of the title; a little bit like the movie Joker (but not so violent because Harleen's past isn't the same of Arthur), which is totally focused on the life of Arthur Fleck, where Joker appears only in the last twenty minutes of the movie.
I'm not saying it isn't a good book (Sejic art made me always crazy), simply it isn't my cup of tea.