If you want to familiarise yourself with the series before reading the review, visit this page, because my Short Book Reviews don't include information about what happens in the books.
Book Four of Riyria Revelations, Emerald Storm, by Michael J. Sullivan, is the best in the series so far. It kept me engaged till the end and managed even to move me to some measure, which is quite a remarkable achievement for any work of fiction nowadays.
There's more action in Emerald Storm than in the first three books, making it a gripping read. Some of the plot twists made me almost hate the author and wonder whether he hates his characters, especially the female ones. Is there truly no limit to the suffering of those poor women? Not that the male characters aren't getting their share of difficulties and pain, but not one of the female characters seems to be struggling towards a happily-ever-after.
Regardless, I would've given Emerald Storm five stars if not for the tediously detailed descriptions of managing a sailing vessel. I know, as a fiction writer, that fiction writers sprinkle their stories with hard facts to make them more plausible, but (here it comes again, the infamous and ominous but) there's a difference between sprinkling and loading. Sprinkling is fine. I don't mind learning a few facts and a handful of new words about a specific subject, even from a fantasy book. However, when I read fiction, I want it to remain fiction from beginning to end, instead of occasionally turning into an instruction manual on anything. I know many epic fantasy readers, perhaps even the majority, like a book the better, the more generous in factual details it is. Yet to me, lessons on fencing, sailing, playing chess, and whatnot are nothing if not distracting at their best and totally off-putting at their worst. The sailing blaah-blaah-blaah in Emerald Storm verges on being off-putting. If the book weren't so damn good aside from the aforementioned bits, I would drop it into my three-star pile.
All in all, I enjoyed Emerald Storm and could scarcely wait to move on to the next book in the series. I'm currently reading Heir of Novron and regret to say that, at least for now, book five, Wintertide, hasn't managed to impress me. Let's not write a review on an unfinished read, however. Who knows what surprises lurk on the pages I am yet to turn, so it would be most unfair to judge the whole book by the first fifteen chapters.