I thought the new edition of Runequest was fantastic, but if it did have a flaw, it's that it was entirely a toolkit with no setting included other than the Meeros sidebars designed to explain the various systems of the game. Well, Monster Island is entirely a setting book, and it more than lives up to the high expectations Runequest set.
The capsule description can be pretty obviously drawn from the book's title. The setting is a lot like King Kong's Skull Island, being a tangled, overgrown volcanic jungle island crawling with dinosaurs and weird monsters, but also draws a lot from Clark Ashton Smith's Hyperborean stories. The island used to be part of a larger continent and the mountain peaks were the sacred Mount Yoormiphazreth where the gods dwelt, until Man Grew Proud, the gods descended to earth for a cage match, the mountain blew up, and everything went to hell, destroying the ancient sorcerous civilization that built the giant causeways that crisscross the island and the Smoking Mirror portals to other worlds that they used to bring in creatures for their amusement or for magical experiments.
The Smoking Mirrors are an especially nice touch, because it provides a great rationale for why the island is crawling will all kinds of incredibly and improbably dangerous flora and fauna that aren't related in any way to each other. Explorers can conceivably find just about anything in the jungles or mountain peaks or seas, and to that end, Monster Island has almost 100 pages of animals, plants, spirits, and weird things to fill out the island. A lot of them are drawn from East Asian or Oceanic mythology, like the Aswang, Manananggal, Nanaue, Rokurokubi, and Tikbalang, but there's plenty of other creatures in there too. The Trifronds, or the allosaurs, with a note that the natives call them "gwangi," or the vorslurp, plus dozens and dozens of others. Even if you aren't interested at all in a new setting, the book is absolutely worth the price for the monsters alone.
There's also a brief section about what sword and sorcery is--focus on human characters with the non-humans being definitely inhuman, the odd and sinister nature of magic, mostly human opponents and occasional weird monsters instead of whole other species--and how to run a sandbox setting, include random encounter charts suited for Monster Island. There's also tweaks to the way Magic Points are recovered such that most of them either come from specific places of power or from the sacrifice of living creatures.
The remainder of the book is about the three cultures of the island--the lizardmen savages, the serpentmen High Folk, and the human colonists.
The lizardmen are divided into stone-age tribes named after their gods--who are also kaiju--with names like the Ghidori, the Gamari, the Gyaosi, or the Kumongi. The tribes live in particular territories, which they don't leave because their tribal shamans perform the rituals that keep the gods asleep beneath the earth to prevent another battle royale between them. Instead, they engage in ritualized warfare to keep their numbers low, but don't wipe each other out because that would wake one of the sleeping gods. Also, they tattoo their deeds on their skins, pass messages through the jungle with giant drum relays, and have a strict division of labor where the young fight or hunt and anyone who lives long enough becomes a shaman.
The High Folk are divided into three cities which spend a lot of their time scheming against each other, but they never manage to gain a hand up over each other because they're also too busy scheming against the colonists and the savages to actually succeed. Also, they're too busy stabbing each other in the back and hoarding sorcerous knowledge for themselves to really actually get much done. Certainly not enough to replicate the great feats of the past.
The humans live in the ruins of one city on the far end of the island. The basic assumption is that it's a trading colony with people from many different lands, but nothing is ever detailed so it's equally possible for them to be shipwrecked sailors or castaways who came through the Smoking Mirrors and banded together for survival. The colony is ruled by a governor, but a lot of the power is held by the various cults of different gods brought from overseas. The gods are pretty explicitly hideous Lovecraftian (well, actually Clark-Ashtonian) entities, and include Thasaidon, Atlach-Nacha, Tsathoggua, and Ubbo-Sathla.
This is a really good example of how to use the Runequest rules to create cultures and implement the magic rules. The humans have Theism, the High Folk have Sorcery--with changed spell names to fit the setting. Hide Life becomes Ensconce Vitality, Regenerate becomes Meliorate Maltreatment, Smother becomes Antagonistic Asphyxiation, and so on--and the savages have Animism.
There's also a list of various locations around the islands, like the ancient causeways walked by the ghosts of old warriors, a city build on the underside of a giant carved lizard head, the tomb of a pre-cataclysmic sorcerer, a nest of birdmen from beyond the Smoking Mirrors who worship the ancient power armor their ancestors wore when they first came through, an abandoned mine filled with radioactive gold, a tower with a bound storm demon that lashes the eastern coast of the island with storms, and so on. They're great, especially the bird men with power armor. I admit, I'm a sucker for science fantasy, and lost high-technology is a good sword and sorcery trope.
The whole book drips with ideas, and even if you don't like the actual setting, you'll find plenty in here to use for inspiration. The locations and the monsters alone make it worth reading. After Runequest and this, I'm pretty much in the camp of buying anything Design Mechanism puts out sight unseen.
[5 of 5 Stars!]