I liked the premise (not that "use children as spies" is particularly unique) and from what I saw here and there, I was expecting the CHERUB series to top Alex Rider.
Unfortunately while the story itself wasn't bad, the writing was... well. I'll try to be kind and assume that it was written either for 8-year-olds (although all the drinking, smoking and snogging puts the target group firmly above that age) or for struggling readers. All tell, no show; flat characterisation; extremely simplistic style; short (and boringly written) sentences.
Not a series I'll be buying or reading more of. A pity.