This guide reads like a textbook -- the boring kind of textbook that Mr. Von York made you read in 10th grade world history, not a fun and interesting textbook. Maybe it's primarily meant as a supplement to the Skulls & Shackles adventure path, but that's not what I had gathered from the product page.
I run a nautical campaign. I wanted some original and inspiring ideas for islands that my players could visit, adventure seeds for a nautical campaign, and interesting character and encounter ideas. I got very little of any of these.
"Detailed entries on more than 20 of the Shackles’ most dangerous and mysterious islands and islets, each with numerous plot hooks, helpful or treacherous NPCs, and unique locations for brave adventurers to discover and explore."
This is where the majority of the bait and switch comes in. Every single plot hook, NPC and interesting location is mentioned in passing, with one to two sentences dedicated to it. If you're looking for more than the tiniest inkling of seeds, look elsewhere.
"Stat blocks for each island, detailing the region’s notable settlements and denizens, as well as possible plunder and resources, such as hidden harbors and shipwrecks."
Not particularly useful. Plunder and resources are simply short lists of good types, such as 'Furs, gems, gold, baby teeth.' There's no trade routes, suggestions on how such goods can be plundered, etc.
"A huge bestiary of new monsters and villains that roam the islands of the Shackles and the high seas around them, including the three-headed lusca, undead pirates and ghost captains, and the degenerate kuru cannibals of the Blood Queen."
Maybe it's because I'm not a fan of the flumph or ridiculous monsters, but the bestiary entries didn't do much for me. I will use the duppy, pirate and draugr blocks and the rest will never see the light of day -- especially the three-headed shark.
"Stat blocks for a wide range of seafaring NPCs, from humble deckhands and smugglers to pirate captains and shipboard sorcerers."
Seven. There are seven in this wide range.
The saving grace of this book is the half-page about ghost ships of the inner sea. It's great, but not so much that I don't regret spending $14 on the PDF.
Also important: There is ONE MAP in this product, depicting (poorly) all of the islands in the Shackles. If you are looking for excellent maps of individual islands, this book is not for you.