"I'd only read a bit of the first book. And I just knew about all the media furor over it. But I'd not read books 2 or 3. I'd just read a bit of it. And I'd seen the films"

David Thewlis is describing the Harry Potter series. He is saying that he had just check out a bit of the first book and understood the media attention it had actually gotten, but he had not read the 2nd or 3rd book. He had just read a bit of the very first book and had seen the movies. This recommends that he was familiar with the story and characters, however had not check out the whole series. It likewise implies that he was more thinking about the films than the books, as he had only check out a bit of the very first book. This might be since he found the movies more entertaining or since he was more acquainted with the movies than the books. In either case, it is clear that he recognized with the Harry Potter series, but had not check out the entire series.