As far as I know they are not putting out three novels per cycle anymore, but rather one novel per cycle, followed by a Planeswalker novel, then the next cycle. So, yeah,
Alara Unbroken is the one book that covers the entire Alara block.
There's an article with general information as well as a list of all novels on Wikipedia
http://en.wikipedia.org/wiki/List_of...thering_novels