The game does not directly specify who the narrator is, but there are suggestions he is Esther's husband and that she is dead, killed in an automobile accident.
Possibly the narrator's wife, but nothing more is known about her. The game wants you to make your own conclusions and guesses.
Paul the Apostle; Later in the game, the readings begin to allude to the story of Paul on the road to Damascus, which is also the subject of some of the graffiti found painted on the cliff walls.
Person who charted the island some time in the past.
A eighteenth-century shepherd and hermit.
Monologue fragments are triggered as the player reaches certain locations in the game; each one is either random, or specific to the area the player is currently exploring. This random selection of voice-over parts causes a lack of coherency, and forces the player to draw their own conclusions.
What you see and hear is completely open to your own thoughts and ideas, and it’s never clear as to exactly what’s real, what’s ethereal or mysterious, and how much of the obfuscation is played out in reality or solely within the protagonists head.
Source #1 Source #2
And let me quote some of the official info about the game that developers mentioned:
What is the significance of the aerial - What happened on the motorway - is the island real or imagined - who is Esther and why has she chosen to summon you here? The answers are out there, on the lost beach and the tunnels under the island. Or then again, they may just not be, after all...
Basically the whole game is made so players can draw their own conclusions as i already said.