Fiction writing rocks

While certainly a great deal of the writing work I do is based to a certain extent on reality...papers for history classes, news blogging opinions, etc....and there is an entertainment value for me, as an author, to write that material...thee is a great deal of fun to be had in the writing of fiction because the rules are easy to break...in fiction writing, there really are no rules.
Take for example the James Joyce attempt to play with time and simultaneity wherein Joyce randomly bounced back and forth between scenarios and conversations in an attempt to "show" simultaneity. It was rather jarring and hard to follow...if you cared enough to try to follow. I have read some of that writing and frankly don;t find it worth the effort. Others do. And Joyce was freed from the bounds of concluding a scene before venturing to another by the nature of what was trying to be accomplished.
In fiction writing...there are no rules. I can play with simultaneity, with time, space, linear action...take, for example, time travel. It has long held fascination for people as it presents the option to disrupt linear action. HG Wells examined the potential for altering the future by changing the past, the Simpsons based an entire Halloween episode over miniscule changes made by Homer, and science fiction is replete with examples of time travel. Movies, too...the entire premise of the Terminator movies, for example...and Time Cop...and others.
All the time travel fiction I have seen assumes that actions in the past change the future but as a fiction writer, it does not mean I am bound to that principle. Let us assume, for a moment, I wanted to write a book about time travel via magic as opposed to science. Most fantasy novels assume that at some point magic existed and disappeared as technology developed. So let us assume that instead of technology advancing (or perhaps alongside it) magic advanced.
Time travel became possible. Now let us set the scene where wars are commonplace. Wizards have become scouts: they can travel to the future and see what the outcome will be from any possible course of action. This allows the commanders to change their actions to a more positive action before the negative actions occur. However, because their actions change, the potential actions for the opponents change...which then changes the possible outcomes.
Now I can set any rules I wish. It could be that a trip forward tires a wizard out, so only so many potential outcomes can be investigated...or I could set a rule that a more powerful wizard could warp the understanding of a perceived outcome...or I could allow them to battle in the future to disrupt actions in the past...basically, if I can conceive of it, I can write it.
More importantly...because I created the rule, I can break it. For example, let us say I am writing a book in which wizards can examine 3 possible outcomes. I have, for example, demonstrated the rules earlier in the book that a 4th trip will kill a wizard and that once they examine 3 outcomes, one of those MUST happen. You , the reader "believe" mu integrity as an author...you "understand" how this fictional world is put together and what is possible in this world.
Is it a betrayal of the reader to then abruptly change the rules? Can I have a wizard who can see AND GUIDE events, but only after his fifth trip because he has a great comprehension of how events are put together? Or is it just me, as an author, invoking artistic privileges?
Sometimes these rule breakings are good. Other times...not so much. Weis and Hickman wrote the DarkSword trilogy, a well-realized world where everyone has some degree of magic...magic is Life. For 2 and a half books it is this way. It is about Joram's search to regain his legacy as King, though he was born without Life (he has NO magic in him...he "breaks" the rule.). Then, at the mid point of the 3rd book...it breaks down and becomes a war between the dwellers of this world and people driving tanks and firing lasers.
Huh? I invested 1500 pages of reading for you to change the rules? Yet...it fits. But it disappoints because never again can I read a book based in that world I enjoyed.
Ah, the conundrum...does the book belong to the author or the reader? Neither? Both? Well, I think....