Although this series is written for children, there's a lot for grown-ups that children wouldn't get. At times hilarious, this series had me laughing out loud in several occasions. It helps if you can understand German, Russian, Spanish, Latin and Welsh (oes, Cymraeg!) as the author has sprinkled phrases in these languages liberally throughout. It's worth taking the time to translate these as one or two contain some of the best jokes.
The series is really one, long story and the later books have several references to characters and events from the earlier ones. So it's best to read through this series in order.
I thoroughly enjoyed episodes 1 to 5 and can't wait for the sixth.