Anthony Horowitz is an English writer who has written more than 40 books.
He is an amazing writer and has captivated his audience for decades.
As he writes both young adult and adult fiction he allows his audience to age and mature and still enjoy his books.
Yes and that allows him to get a following that starts from a young age to an older age
If you enjoy tv you can catch his work in Poirot and Midsomer Murders.
I have not read those, I am guessing those are more geared towards adults?
Yes, they are more for adults as they deal with murder and crime scene investigations. 
That is amazing that he is able to switch genres and keep up the level of involvment.
The Power of Five series looks amazing, it's been described as Alex Rider but with witches and devils.
You have really educated me on an author as I child I loved, I did not know that Horrowitz still wrote and to this level.