“World Tree” is a thoroughly developed fantasy world. There are cities on branches miles wide and thousands of miles long, with people looking down into space and trading with flying ships. Magic is so common that even children use it, and you learn how it’s used in ordinary life and not just adventuring. The races aren’t just dog-men, otter-men, etc. — they have unique customs, personalities, clothing, and architecture. Metal is rare, so wood and bone tools have become extremely advanced. Meddling gods look down from the sky.
The book’s first hundred pages suck you in and make you want to play in this world, even before you see the rules and huge magic list. There are explanatory notes and one-page stories throughout the book written from the characters’ perspective; these are useful and often funny. Even if you’re not a gamer, it’s worth reading. Writers can learn from this great example of world-building.
The rules are fairly simple, since most rolls are (Stat + Skill + d20) versus some number, though filling out a character sheet can take a long time due to the variety of spells and skills and the odd experience point system. The spells explore all combinations of the 7 magic Verbs and 12 Nouns (e.g. “Change” + “Flesh” = shapeshifting) and let you do many things in multiple ways. There are eight fully playable races with different specialties from the fast, shape-changing Orren with “species-wide ADD” to the physically puny but immortal and magically-gifted Zi Ri, to the armored insect Herethroy who use huge three-handed swords.
This is no generic medieval game with elves and dungeons; it’s a complete world. Beware when reading, as I’ve seen people forget what time it is and where they are!