Rectangular. I haven't tallied them, but something like half connect on all four sides, while the others connect only 3. They are placed face down and then flipped when a knight lands on one to explore it. There are two halves to the tile array, each with its own set of tiles - the Earthly Wood and the Enchanted Wood - but this has no mechanical effect except (i) to guarantee that certain locations named on the tiles will always be in one or the other half (eg the Cave is on an earthly tile, while the Palace and Island are both on enchanted tiles), and (ii) to allow the board to be described in "mirror" terms (ie this earthly tile is the mirror of this enchanted tile) which is then used for teleporting and the like.
When a tile is flipped, it is revealed to be either a path or a clearing. If a clearing, a card is chosen from the "denizens" pile, and depending what it is the relevant resolution rules are invoked - there can be fighting, reaction rolls (which can be modified by stats, but there is no "negotiating" or free roleplaying with NPCs) or the standard sorts of spell effects one would expect in a romantic fantasy game (ensnared by an enchantress, lost in a mystic fog, etc).
There are only a few "monsters": wild ox, wild boar, saracen, troll, giant and orc; and interestingly, the orc is the most fearsome. The other NPCs are what one would expect - kings, princesses, hermits, Merlin, an elf, a dwarf who leads you to magic armour, etc.
I don't play a lot of boardgames, and so am not drawing on much experience, but based on my solo playthroughs I would expect a game with four players to take a couple of hours. I haven't played the new D&D games (Ravenloft etc) - I only know them from what I've read at the WotC site, plus a couple of reviews and actual play posts. But my feeling is that Mystic Wood would be a bit more languid and a bit less intense in the way it plays (in some ways much like the difference between 1970s/early 90s RPGs, and contemporary ones).
