I read this book to my 10 year old son and we both enjoyed it as much as the other two books. Sebastian, Cornelius and Max adventure to the jungle of Mendip, meet yet another woman (poor Sebastian!), and encounter and defeat lots of monsters all with the ultimate aim of finding a lost city and piles of treasure. We enjoyed the jokes. We enjoyed the characterisation. All these books are rollicking adventures with a good bit of humour, no boring bits, and no "dark" bits, despite the lead character's surname!
One tiny gripe I have is with the editors (or maybe even the typesetters): in one or two places the punctuation was incorrect, and in one or two places a sentence didn't flow well. This book was so good it deserved the best editing!