Updated 05 April 2004, 14.44
The Spiderwick Chronicles are a series of six books which have been huge in the USA, hot on the heels of Potter, Artemis Fowl and LOTR.
They follow the faerie-filled adventures of the Grace children who have moved from the city to a big estate with lots of spooky secrets.
Holly Black and Tony Di Terlizzi (author and illustrator) were in the UK on their first big book tour when Newsround's Jo Twist caught up with them.
Who are the main characters in the books?
Holly: Well, there is Jared, Simon and Mallory Grace. Jared and Simon are twins and they are nine, and Mallory is 13. Jared is the troublemaker - he is always in the wrong place at the wrong time. He has a bit of a temper too, which doesn't help.
Simon is the exact opposite - he has very little temper. He loves animals. He is good at school, while Jared is not as good.
Tony: Their family is going through a separation, and so Jared is a little more aggressive than he would normally be, and Simon is maybe a little more withdrawn because of this.
Holly: Mallory is really into fencing, and very fed-up with her little brothers. Their dad moved to California and their mum felt she could not keep up the city place.
She wanted a new start for them, so her mother arranged it with their crazy old aunt Lucinda to take over her place, the Spiderwick estate, which was really in need of people.
So how do they get mixed up with faeries?
Brownies can sometimes turn bad
Holly: When they get there, there are weird things going on in the house. The children come across a book which gets them into more trouble.
Tony: They find a secret study in the house, which turns out to be their great great Uncle Arthur's hideaway. He's been doing an intense study of faerie folklore and mythology, and faerie meaning anything like a mammal, so they could be sprites, trolls or goblins.
The first faerie they find is a boggart living in the house, which is a house brownie gone bad.
So how important are faeries in the books?
Holly: Well, to start with, we were contacted by the Grace kids who gave us a book about Spiderwick estate. They are real kids - we have just changed their names.
We have both done stuff with faerie folklore before, so that's why they specifically came to us.
We were annoyed with the way faeries are perceived as girly, glittery, tiny and pretty things when really they are, in folklore, quite diverse and some of them are dangerous.
Tony: I love the original fairytales, and I think a good one is always half dark and half light. Old fairytales were more like that, Pinocchio, Alice in Wonderland, Grimm's Tales.
Jared on the cover of the second book of the series
Do you believe in faeries then?
Holly: I have never seen any faeries personally, but I think there are more things than we can see.
Tony: Humans are quite a young species on the planet, and there is a lot of it we don't understand. We rely only on our five senses. If we can't see, hear, touch, feel or smell it, we think it doesn't exist.
So can anyone earn the right to see, to have the Sight? In the books, there is a seeing stone isn't there, which the children can see faeries with?
Holly: There are certainly people who are born with "the Sight", like those who are born with red hair. And there are different ways to get it too, with faerie ointment, carrying four-leafed clovers, that kind of thing.
Or if you are in-between time, like dusk and dawn, you are more likely to see faeries. Or as a teenager - you are not quite a child and not quite an adult - you are more likely to be able to see them.
Holly grew up reading everything but is a faerie expert
There are a lot of comparisons made with your books and the Potter books, His Dark Materials and Artemis Fowl - do you mind that and what are the differences?
Holly: I have just read the first Artemis Fowl book - and there is certainly room for comparison, but he has a fun, different take on technology which is really cool.
Tony: The last Harry Potter book was 700 odd pages? That is for quite an older audience.
Holly and Tony have always liked faerie folklore
Are you excited about the film?
Holly: I think it will be fun. I don't know how much it is going to be exactly like the books. I just hope it is a really good movie.
Tony: That's what we told them - it didn't need to be exactly the same as the book. It is being written by the same guy who wrote Elf, David Berenbaum
Holly: From what we have seen so far, he has really captured the kids' personalities - he really knows them.
There are going to be a lot of special effects obviously, how do you feel about that?
Tony: Our wish is that we'd love it if it was less CGI animation and more Jim Henson's creatures - that's what we grew up on.
Holly: People act much better with puppets.
Tony: Yeah, like in the Phantom Menace, you have Liam Neeson talking to a ping pong ball, so they looked through the CGI characters. But if there is something actually there to work with, it is more a believable performance.
Tony did illustrations for Dungeons & Dragons and JRR Tolkien book
How do you think the Potter and Rings films turned out compared to the books?
Holly: I have seen them all and thought they were all really great - I will probably see them all again.
Tony: I was a little disappointed with the Harry films because they were almost too loyal to the books. In the end, they just translated them.
They are all beautiful movies and looked amazing.
The LOTR trilogy is the best ever.
But Tolkien sells second to the bible - that is heavy duty anyway. As good as I think we are... (laughs)
The emotion in our books will be the key to the film, people are going to feel something when they read the books and if they can pick up on that, that's great.
Finally, what advice do you have for children who want to go into writing or illustrating?
Holly: Just read everything - not just fantasy books, but magazines, everything. And write - write a lot and don't worry if it is any good or not.
Tony: I kept a sketchbook journal where I would draw and write. I also copied people that I liked when I was kid. Artistic and technical ability can be learned through just doing it.