Dear Esther is more of an experience than a game. You walk though it, learning the fragmented story as you go. Apart from movement, there is nothing to interact with. You simply explore, listen to the story and enjoy the beautiful surroundings.
From a gameplay perspective, Dear Esther is unusual. It's almost interactive fiction, except there's no interaction apart from the act of exploration. There is no jump, no fire or action button, just direction controls. The environment, although at first it looks open, offers minimal freedom. You are free to move forward at your own pace.
Where Dear Esther excels is in graphics and sound. The story is well narrated as you progress, and the soundtrack and effects are stunning. The setting, a remote island off Scotland is beautiful - perhaps only Red Dead Redemption has done countryside this well. But it's the caves you enter that give Dear Esther its 'wow' factor. Covered in phosphorous material, they are otherworldly glowing spaces that you'll enjoy simply exploring.
Dear Esther is quite short, and while you may want to replay it to see if you missed anything, one play through might be enough. It's very linear, so there's not a lot of room for differing experiences. Despite this, Dear Esther's story is memorable and there is enough ambiguity to make you think about what it all means! Who are you? Is the island real? What's the significance of Wolverhampton?
These questions, and more await you in Dear Esther, and I really recommend you play.