As the title implies, INVASION finally chronicles the long-expected attack on Dominaria from the Phyrexians out of Rath. If that sentence doesn't make sense to you, this book probably won't either. To get the full story is no simple matter however. You should start with the anthology Rath and Storm, then go on to the Artifacts Cycle (including: The Brothers' War, Planeswalker , Time Streams, and Bloodlines), followed by the Masquerade Cycle (including: Mercadian Masques, Nemesis, and Prophecy). Finally, if you really want to get the full story, read the prequel The Thran. Then you'll be up to speed with the story so far. Some of those books are good, most are only decent, and a couple of them are down right bad. So you'll have to make up your own mind about whether you're willing to give this story as much time and attention as it demands. I'll tell you that the only reason I have kept with it so long is that I simply can't admit defeat and not finish a story. Also, I am a glutton for punishment :)..
Anyway, INVASION finally tells the story of the Phyrexian attack, which is something we've been anticipating and preparing for over the last bunch of books. With so much build-up priming my appetite for this book, I couldn't help but being somewhat disappointed in the execution. While it is undeniably exciting, with plenty of action, dramatic events, and highly emotional moments, the story just didn't live up to my hopes. The characters behave completely predictably, many parts of the book seemed rushed, and too much of an effort was placed on telling about every part of Dominaria. With a very limited amount of space, King tried to tell a hugely complicated story that involved nearly all of Dominaria and many central characters. The result is a hectic and off-putting reading experience.
That being said, the story is still not complete, with two more books in this trilogy apparently detailing further battles between the armies of Phyrexia and Urza's defenders.