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.

I seeded it with plot hooks, mad rambles, gibberish and prophecies.

The strange thing is, the players are fulfilling those prophecies all by themselves now by actively pursuing them...

It's not as satisfying, but you can always just use mechanics to abstract it. Succeed on X lore check and you gain a +10 bonus to Y check in the future because you've received clues about what will happen later. Not as much fun, but it doesn't require you to be clairvoyant so it does have that going for it.

the one game that I used it the players burned it as soon as they left the temple, they assumed that it was some sort of trap. The keeper of secrets bound within it's pages was mildly annoyed, but glad to be free so gave them each a roll on the mutation table and left.

Well, this is how I so far have decided to use it:

If I just let them read the book for hints, they will keep trying to read it to get more information, which will force me to keep improvising stuff, which often doesn't lead to the best snap decisions. I need some time to prepare cool stuff like that.

So, in order to gain soemthing usefull, a person has to study it over several hours with a series of difficult skill rolls in order to glean something of use from it. If he aborts before succeeding, he has to star over. There are risks involved with failing rolls, to studying the book is not something you would want to do until you have run out of more mundane options.

So I've just made a list that I will pad out over time of vague discriptions of places or events that I can alter to fit whatever goals the group has. For example, if they are looking for an artifact; I could have them find a referance to something that sounds like the artifact in a story about a city of impossibly tall towers and unquestionable laws that ends with towers toppling and others rising. Which leads them to the adventure in the Tome of Fate.

Indeed. It's a good 'plot hook machine'. You could also have it contain a partial copy of the Hand of Corruption ritual.