Okay, haven't played ACII in a while so please bear with me if I flub-up or am totally off mark with this comment. If I am please state so and I will make apologies as appropriate...
So, ACII is about your guy Ezio runnin round murderin people who deserve it for the "greater good" and because he's told to do so. I liked it a lot better than the first one, which just had a ridiculous amount of land to cover for the goals. Very polished in graphics but omfg the distances I had to run since I forgot to get on my horse half the time! Okay, back to ACII since that's what the topic is about >.>
I remember killing one of the Borgias, I think? Or was that one of the Medici? I feel like it was a Medici since they had a very heavy influence in Italian politics and religion... but not sure. So, there's the general connection to the holiest of holys, the great and powerful Raptor Jesus. So, we run around killing prominent figures in Italian history, through Vienna (so nice a city with its canals), and several other places... I would guess Rome but again haven't played for any length of time since I beat it a month after it hit the shelves.
The Animus machine, being the connection to the past that is necessary for the plotline of the series, is unique. It is only unique in the way that it is used, I think. The Animus doesn't actually let you "change" events, concerning the plotline, but lets you experience them the way they are required to happen since it is just a genetic memory. Oh, another consideration is the entire premise of Genetic Memory. That has been around for a while, and is most often associated with migrating birds, and fish such as Salmon which return generation after generation to the same calm portion of stream year after year. But back to the Animus... I have not read the book nor any synopsis about it, and so cannot say what, if any, relationship there is between the machine/object/whatever in the book and the Animus machine. Assassins are in a lot of movies (Ninja Assassin, etc), games (Hitman, etc), other books (essential the Splinter Cell series is about a spy/hitman/F'ingAwesomeDude... pretty sure Splinter Cell is a book series anyway >.>), and the greatest argument HISTORY!, so it is impossible for the auther to claim that assassins are an original idea.
The Brotherhood of Assassins is something that I honestly find unique and refreshing. If there is something similar to a 'Brotherhood' in the book then maybe the author has a very small possibility of getting some sort of payout... but not likely.
Overall, I think that this is just a ploy for attention similar to the link provided earlier in this thread wherein J.K.Rowling was sued over the Harry Potter series. But, also stated earlier, the burden of proof rests entirely on him. At least as far as the US code of law is concerned. The Accused is innocent until proven Guilty, which rests burden of proof upon the Plaintiff and not the Defendant. There is much room for reasonable doubt in this case, and as such unless Ubi's lawyers really have to work at the case (doubt it) there is little more to do than wait and countersue for the legal costs which will most assuredly be given for such a stupid lawsuit.
GalenEvil