If I had to describe this game in one word, it would probably be either "stupid" or "confusing." Really it's a bit of both. Now that's not to say it's a /bad/ game. Honestly, it's kinda complicated.
Let's start with the story. It's interesting enough, albeit rather short. You play as the protagonist, who is revisiting an old sawmill in search for someone named Anna. There are three possible endings, each giving different amoutns of information as to your character's past depending on how you play it.
Next, the gameplay. Here's where it gets bad. The game is played in a first-person perspective, and you move around and interact with objets, similar to Amnesia. Except the controls in Anna are extremely inefficient and poorly designed. Want to pick up an item? Click it, then click "pick up." Want to use it on something? Open your inventory, find the item, click it, click "use," close the inventory, then click on the thing you want to use it on.
Then half the time it doesn't work. So you have to try the item on something else, or try another item altogether. This goes on for and endless period of time until you manage to find the right combination of items.
Which brings me to the puzzles. The wonky controls wouldn't be so annoying if the puzzles made any kind of logical sense. But many of them are not only extremely vague, but completely random as well. I kid you not, one of the puzzles requires you to take some sawdust and throw it in a pool of water, which reveals an invisible bridge that you must then walk across, use a lighter to heat up a ritual knife, and then cut yourself and let the blood drop into the water. And while the game gives some hints as to what you need to do, they are vague and make it almost impossible to figure the puzzle out yourself in less than half an hour. My first playthrough of this game took over two hours, and that was with me consulting the walkthrough every ten minutes. Once I knew what to do, I completed a second playthrough in less than half an hour. That should give you an idea of where most of the playtime comes from.
All in all, was this a bad game? Not entirely. It's not what I'd call poorly-made; it has some interesting features, and the sound and music are actually very impressive. But the controls are frustrating, the puzzles makes no sense, and the few times the game tries to scare you, you're often just happy to see that you finally got something right rather than scared. If you like atmosphere, and can stand to lose a few hours of your life, then you might as well get this game, preferably when it's on sale. But it's not something you'll walk away from with a feeling of satisfaction.