The first collectible is Manuscript pages, which there are 106 of total in the game. You can read them and they all form together to make a book. In gameplay, reading the Manuscript pages show what fore coming events are going to take place. Some of them talk about story specific instances, other ones are hints of what's going to happen in the far future, others yet just give insight to what is happening to the survivors of Bright Falls around you. However, and what adds a bit of interest, is collecting some Manuscript Pages will trigger certain events and ambushes to happen, others will give details of a secret you can find. These are the most common collectible, some are out in plain site, others a little exploring is needed. However, you can't collect all of them in one playthrough; several of the Manuscript pages can only be found in Nightmare Difficulty which must be unlocked.