I often here it compared with LOTR, but the two are so unbefitting of comparison. More like contrast. The moral ambiguity, enormous amount of characters and their depth, combined with GRRM's atypical follow threw on threats to kill characters makes it one of the most gritty and mature books I have ever read, in spite of the low-fantasy stereotype that is so stagnant and polarized in other stories.
I perticularly like the fact that there is no clear protagonist or antagonist. It like the saying goes "history is written by the victors" except the history hasn't been written yet, so there is no good or evil.
The book first and foremost is a political intrigue and suspence story. The fantasy elements mostly add flavor to the main plot, rather than being the focus like in the vast majority of other fantasy.
I highly recommend it.
PS the prologue gave a false impression.