At its simplest level, manuscripts are about building "memory assistance devices". However, there are some rudimentary devices you should start with:

• tally sticks, which are marked with notches ("tally marks")
• knotted rope, with the number of knots recording a number

Manuscripts

• writing medium
  • simple
    • Write on planed wood, or clay tablets, but they're too thick to stack. Better is birch bark or dried palm leaves.
  • wax tablet
    • make a tablet of wood, and coat it in wax. Write on it with a pointed stick. A razor-like straightedge can be used to smooth over existing writing, allowing it to be reused.
  • papyrus is available in certain parts of the world (Africa and the Levant mostly), but not available in most other areas
    • The top of the plant looks like a "feather duster". It's found most abundantly in swamps, shallow lakes, and along stream banks.
    • the outer hard part of the plant's main branch is stripped off, and the soft inside is cut into strips. The strips are laid in rows (in the shape of a sheet), and then a second layer is laid on top, perpendicular to the first layer. The two layers are soaked in water (to increase adhesion), then they're hammered together to form a single sheet, and dried under pressure. The sheet is then polished with a rounded object (i.e. a stone).
  • parchment
    • the skin of any animal (cow, goat, horse, ...), dehaired in a lime solution, and then stretched on a frame to dry
• ink
  • ...
• bookbinding
  • scrolls can be used, but trying to bend ancient materials is a bad idea
  • better to fold pages in half, sew nested pages into small sections ("codices"), and then sew multiple sections into one book

Later

Later, once memories of the modern world had faded, I'd try to foster my own religion, since that's what the most ambitious fiction writers do.