Overall, I was disappointed with the series. There were too many elements to the story that did not seem to fit together seamlessly - letters, rhymes, hidden objects, symbols and so on. There were also a number of stories that Rosette told to Juliet that were red herrings, and she also insisted that Juliet not listen to the second ghost, Florence, who told lies - but Florence rarely appeared in the story to say anything, lies or otherwise! When she finally did show up, there was no logic as to why she'd been prevented from interacting with Juliet in the first place or why she and Rosette could not meet.
And as for Rosette insisting that Florence was lying, I don't understand the motivation for saying that. I don't understand why she played games with the truth or why finding things out required so many different elements. It all seemed unnecessarily complicated.
As for the relationship between Juliet and Mario, I don't understand what they see in each other. Their relationship appears to be purely physical (lots of kissing) but as for trusting one another and being friends, there's not much evidence of that. There is a lot of angst, a lot of frustration, a lot of anger at times, but no evidence of a solid foundation on which to base a relationship.
Also, Georgia, Juliet's sister, has had some ghostly experiences herself, but that particular thread did not develop into anything in the story. I wonder why?
So, all in all, this was not a satisfying read for me, unfortunately.