Sydney is very different from Rose Hathaway. She is has a high intellect and craves knowledge with modesty and celibacy being very important to her. Sydney is extremely excited to be going to school as she previously hasn't been allowed and takes advantage of this at every opportunity. Being an Alchemist she has deep-rooted views about Moroi and Dhampirs resulting in major trust issues and even great fear at times. Sydney gradually overcomes this as she learns to trust Jill, Eddie and Adrian and even count them as her close friends.
Sydney and Adrian develop feelings for each other more and more during the series. This is quite hard for Sydney at first as the world views a relationship between Moroi and humans to be of the utmost taboo. Over time they overcome this as their love for each other is far greater. Their relationship develops slowly at first which is great to see, they start out not trusting each other at first then slowly they become good friends.
This series is fast past with plenty of amazing twists and turns that I didn't see coming. It expands on the world more and more and even reveal some new mysteries. The series is written really well so that everything flows together naturally. It has great character development and even some reappearances of characters from Vampire Academy.