Haha, welcome to the forum!
I was the same.
Basically, I had gone the local bookstore.. How long has it been now? About 6 years now? [yeah, I have the green cover

] And bought the book because I had loved Groosham Grange and the Unholy Grail. It was soo good! For me, being able to finish that book that day was a big thing, yet I remember that I managed =D
Definitely read the Power of Five series. IF possible, it's even better than Alex Rider, it's that good =]