I'm running False Prophets converted to WFRP, but the question is much the same no matter which setting. How did you guys use the Torestus after the players got ahold of it? It's not like thye can just open it and read what to do next, and it seems like it could be a bit of a hassle to make a whole bunch of stories that are vague enough that they could work like prophesies when you can't predict what the players will actually do.
I am thinking of letting them make some rolls to try to decipher something meaningful from the book which will hint at what they should be doing, but I'm not quite sure just how to implement it yet.