Do not pay money for this game under any circumstances.
Underneath a heap of minor gameplay annoyances that add up to a frustrating experience, Trine is a good game. The platforming elements are decent, and the visuals are truly awe-inspiring. The art direction in this game is stellar, and as such the levels are great fun to look at. The problem is that basically everything else about Trine is frustrating, boring, or both. The game doesn't lack for polish and it doesn't feel unfinished, which makes the gameplay annoyances seem especially odd.
As the platforming is basically the only redeeming quality Trine has, you'll become quickly annoyed with the way that the characters can't seem to move in any direction through the air except up. Tapping the jump button will cause the character to make a huge arc through the air that will land them a maximum of about four feet from the starting point. This makes jumping feel extremely unwieldy, and frequently makes it difficult to make large jumps. Even after getting a running start, it will frustrate you to no end that your character will still jump directly upward and gain almost no lateral distance.
The other major annoyance in the game is combat. Over the course of the game's levels, you will face hundreds upon hundreds of enemies which look EXACTLY IDENTICAL. There is no enemy variety to speak of; the only adversary you will encounter are skeletons carrying a variety of different weapons. The cookie-cutter enemies could be forgiven if the combat were at least good, but it simply is not. You will play three characters during the game, but only two of them - the thief and the knight - have any combat abilities whatsoever. This means that if these two characters are killed, you will be left with a wizard to fend off the hordes of undead with no abilities except a spell which generates boxes and planks out of thin air, which is exactly as useless in a fight as it sounds. The knight's and the thief's combat abilities make them capable in a fight, but unfortunately killing off wave after wave of identical skeletons is absolutely no fun.
If you take only one thing away from this review, let it be this: Trine is a terrible game. It's not one that lacks for polish, and the visuals are stunning. Download the demo first and see if maybe you could get some enjoyment out of it to justify the ten dollar asking price, but otherwise, do not pay money for this game under any circumstances. Never have I so thoroughly regretted spending money on a game.