I can’t think of an exact definition for twaddle but I can give you my understanding of it. Twaddle is anything that talks down to the child as well as any books that are just pure fluff with no depth.
I wouldn’t classify the Series of Unfortunate Events books as complete twaddle. I think they could have their place at a certain reading level.
When I think of twaddle, books like the Captain Underpants books or The Babysitters’ Club come to mind. They write down to children, lack complex sentence structure and rich vocabulary and are just shallow-they don’t provide any meat for the children to chew on-no food for thought.
My son loves the Lemony Snickets’ series, too. It’s not my favorite, but he enjoys books and movies that are dark. They are some of the few books he will read willingly.
I will share that the author’s tendency to define difficult words within the text of the book has taught him several new words. 😉
DH read them aloud, my DS read them to himself, and my DS listened to the audio books incessantly for a while. They are that entertaining to him.