Some people (so I've heard) can do the same thing with writing. Doesn't seem to work out too well for me. Most of the time I need at least five minutes to get into the story's state of mind. At least. (Sometimes a half an hour, sometimes never... :P) If I am lucky enough to have an idea just raring to go, then the tearing myself away part becomes the problem. Nothing quite so painful as ripping my attention from the story world my mind is trying to unfold. With a book, though reading in snippets may be disorienting, at least you know that the words are going to be there when you come back to the page. With writing, well, who can say the same for that?