It ain't bad.

The good: You can see how the GM set up epic events for the characters to stumble through, you can see the good rolls and bad rolls and the GM stepping in to prevent the characters from dying (although they should), and so forth.

The bad: see above.

It's a pretty compelling read, yes. It's also a book where the main characters react rather than act upon. In itself, I really don't mind that - it leaves the "acting upon" to minor characters, and drives the plot forward in a sufficiently interesting and sufficiently different way that I find it acceptable.

But unless you happen to enjoy reading an RPG session log, I'm not sure it's a good plot. There's too much stumbling from bad to worse, and too little in the way of character or world revelations to make up for that.

The best thing, to me, was essentially the epilogue. It hints at greater changes in the factions introduced to the world so far, which may mean for a more interesting #5 in the series.