The categories that the codex contains are

What is the codex. It is a new tab in the adventures interface that contains every book or other readable item you've found and their contents. But you should know that this is just what RS Gold players suggested for the new game content. If you are interested, read the following ones.
The codex can be accessed from anywhere in the world and contains categories to filter books by and a search function that allows you to search by a book's name or by the name of a quest they are involved in.
With the codex, any player interested in the game's lore will have a much easier time to find and read through the texts they've found. Once you pick up a book, note, or any item of the sort, its contents are added to your codex.
The categories that the codex contains are:
Lore & Histories
History of the Order, Malleus Daemoniorum, Voice of the Elders, Legend of the Brothers,etc.
Memories
Mahjarrat memories, Bandos' memories, etc.
Journals & Diaries
Diary of Herbi Flax, Dominion journal, Dungeoneering journals, First Dragonkin journal, etc.
Tablets
Lamistard's tablets, prophecy tabletx, TzHaar language tablets, etc.
Manuals & Guides
Gianne's cook book, Citadel handbook, Castle wars manual, Book of binding, etc.
Notes
Mahjarrat notes, My notes, Scabarite Notes, Valerio's lyrics sheet, etc.
Letters & Messages
Surok's letter, Letter from Brundt, lorwerth's message, etc.
When a player manages to find every single readable item in the game and fully completes their codex, they are awarded with a cosmetic override and an emote. These can be used untill new readable items are released that must be added to the codex.
The override is a large sack of books on your back, with paper falling out of it as you walk. The emote displays you taking a large book from a bookcase and sitting down in an ornate chair as you begin flipping the pages, before standing back up and putting it back into the bookcase.
A really cool idea, like a portable bookcase. But perhaps a bit too unrealistic. However, for the lore-lovers and completitionists, this could be a nice thing to have. What is your opinion? Let 4rsgold know.