This achievement will unlock upon successful completion of the game. Here's what you need to do:
*** Spoiler - click to reveal ***First, head around the island and flick on every switch. There should be eight of them scattered around the island near all of the linking books and one by the Mechanical age book. Once all of them are on, go to the marker switch on the dock and flick it off and it will open up revealing a page. Now head to the library and go inside the fireplace, replicating the pattern as instructed by Sirrus and/or Achenar (you'll need to find the four blue/red pages hidden in the ages). Once inside, you'll find a green book. Link into it and give the page to Atrus to complete the game and unlock this achievement.