Book 3 is real! Or at least a page of it is real. Patrick Rothfuss read the prologue during some kind of stream or something.
Here's a reddit thread with the details of the stream.
And here is the transcription of the prologue (from here):
It was still night in the middle of Newarre. The Waystone Inn lay in silence, and it was a silence of three parts.
The most obvious part was a vast, echoing quiet made by things that were lacking. If the horizon had shown the slightest kiss of blue, the town would be stirring. There would be the crackle of kindling, the gentle murmur of water simmering for porridge or tea. The slow, dewy hush of folk walking through the grass would have brushed the silence off the front steps of houses with the indifferent briskness of an old birch broom. If Newarre had been large enough to warrant watchmen, they would have trudged and grumbled the silence away like an unwelcome stranger. If there had been music… but no, of course there was no music. In fact there were none of these things, and so the silence remained.
In the basement of the Waystone, there was the smell of coal smoke and seared iron. Everywhere was the evidence of hurried work: tools scattered, bottles left in disarray. A spill of acid hissed quietly to itself, having slopped over the edge of a wide stone bowl. Nearby, the bricks of a tiny forge made small, sweet, pinging noises as they cooled. These tiny forgotten noises added a furtive silence to the larger, echoing one. They bound it together, like tiny stitches of bright brass thread, the low drumming counterpoint a tabor beats behind a song.
The third silence was not an easy thing to notice. If you listened long enough, you might begin to feel it in the chill copper of the Waystone’s locks, turned tight to keep the night at bay. It lurked in the thick timbers of the door and nestled deep in the building’s grey foundation stones. And it was in the hands of the man who had designed the Inn, as he slowly undressed himself beside a bare and narrow bed.
The man had true-red hair, red as flame. His eyes were dark and weary, and he moved with the slow care of a man who is badly hurt, or tired, or old beyond his years.
The Waystone was his, just as the third silence was his. This was appropriate, as it was the greatest silence of the three, holding the others inside itself. It was deep and wide as autumn’s ending. It was heavy as a great river-smooth stone. It was the patient, cut-flower sound of a man who is waiting to die.