Deliberately so in the books. Enjoyed the TV versions but they don't quite catch the tongue-in-cheek of the novels.
I'm planning on reading at least one of the books, so I'll found out what the differences are.
You need to read them as if Atkinson is saying 'now how can I make the next step even more preposterous'. She's got a wicked sense of humour and the characters are beautifully drawn. I loved the relationship between the Scottish girl, the professor and the baby in one of the novels.
The films miss out one of the daftest concepts - Brodie is bequeathed a fortune by a strange woman at the end of book 1; by book 3, after relocating to France, he's lost it all after marrying a woman who promptly absconds with all the money. You just have to suspend your disbelief and enjoy the ride - a bit like opera!