As a reader you recognise that feeling when you're lost in a book? You know the one - when whatever's going on around you seems less real than what you're reading and all you want to do is keep going deeper into the story whether it's about being halfway up a mountain in Brazil in 1823 of in love with a man you aren't sure you can trust or fighting a war in the last human outpost, somewhere beyond the moon. Well, if you're writing that book it's real for you too.