My daughter really enjoys this series and frequently rereads them. They’re remarkably hard to get hold of in the United States, though, especially in hard copy! We ended up ordering our copy of Star Style from the UK. They are occasionally available through Scholastic, often as parts of sets. Many of these titles are now available on Kindle and you can sometimes get the hard copies through Amazon or Barnes & Noble.
Here are links to my reviews of the series:
Because I’ve found it hard to keep these straight, here’s a list of the My Sister the Vampire books in order. The titles in parentheses are the US titles:
5. Take Two
6. Love Bites
7. Lucky Break
8. Star Style (The Bat Pack)
9. Twin Spins (TwinTastrophe)
10. Date with Destiny (Bite Night)
11. Flying Solo (Vampire School Dropout)
12.Stake Out! (Read It and Creep)
13. Double Disaster! (Fangs for the Memories)
14. Flipping Out!