Hello.

I decided to "join" talkmagic to add a note about my (and Timon's) work. I'm not from the UK so I won't bother you more then a little.
Grue's percentages are just about right, although the book goes over one way that I always use to avoid memory.
I want to add that none of the traditional methods are used in it. I am aware of Technique, as released by PaperCrane, and I can assure you that it is not that effect.
I have only been using Air Writer (and it's predecessor, MMD), for a few weeks because they are entirely new. I've sent it out to at least a dozen people and everyone of them has has vouched that the method is entirely original. I wouldn't want to take someone's idea and resell it as my own.
The Air Writer does take practice, but there are ways as Timon discusses in the book to keep it almost entirely surefire while you practice this, and then move up to more adventurous routines.
I've probably already said more then you wanted to hear, but if you have any questions, feel free to ask away; as the primary creator I'll be able to answer most of them.
Cheers,
DekEl