this film's premise is similar to The Vampire's Assistant (trailer & clips here), the first film adaptation of Darren Shan's Vampire Blood trilogy (the first of 4 trilogies in his fictionally biographical Saga of Darren Shan arc).   Assistant had some great story elements, a lot of humor, and occasionally stellar special effects work; it was entertaining, but short of outstanding.   not having read the books, i can't comment on them personally, but i gather J.K. Rowling liked them.
Apprentice looks like it had a lot higher budget- your typical Disney summer blockbuster / family-oriented action-adventure film.   i was skeptical but, judging by the trailer, this could be fun.