How's it work? ICly your character acquires a book/tome. They're left in piles in every major city, so you could just pick up one that way. You could buy it from some get-rich-quick goblin (wait, redundant!). You could find it on a dead body. It can fall from the sky and hit you on the head. Anything works!
If someone sold it or gave it to you, they likely told you what it is: A magic book that permits you to communicate with anyone else who has one. The book translates all languages (so yay cross faction RP!). If you found it, your character will likely jot down a note and might be surprised when "the book" replies.
It's that simple on the IC end!
One of the biggest worries a lot of folks have is they never used Twitter before. I hadn't, previous to the IC project. It's easy as pie to learn! Just go to www.twitter.com and make an account. Your account name will be your "book name" that everyone will know you by. You can use your character's real name, nickname, job, random words, whatever. I use @Sunthistle for my character Mikha Sunthistle, but @SteadfastShield for my more security-minded paladin.
ICly the book has two parts, the front and the back. The front pages are public tweets -- anyone with a tome can see them. The back pages are PMs (for some reason Twitter calls PMs DMs, but it's the same thing: A private message to one person).
New folks who learn about the IC Twitter Project through the official forum have a hard time finding active folks (it makes me sad how many potential new folks we must lose due to lack of contact). However, it's not hard to make contact with others! Just go to an active person's feed and check out who they follow.
Mine is: https://twitter.com/Sunthistle/followin
Sego's is: https://twitter.com/SegoRyder/follo
You can go through either or both of those lists and follow them all. Your book just magically adds folks on its own, so no need to reason it away ICly.
However, you can ICly control who is in your book as well. ICly, the very last page of your book is a list of all the people connected to your book, so you can strike a name/cross it out to remove them, or write a name in.
This is getting long and I don't want to overwhelm folks. It's just such a great tool for RP, I get excited talking about it. :) I'm approaching 20,000 IC messages through Twitter over about two years! I've found endless RP though it, made great friends, and just had so much fun. :)
Shy about approaching people in game for RP? It's easy to meet people through the book and then set up in-game or IM RP later!
Want to RP with people on another server? Anyone can join, we have active members from many other servers! It doesn't even have to be someone on a RP server. It doesn't even have to be someone with an active WoW account! Former players can keep IC ties with the help of the Twitter project.
New to RP? This is a great way to dip your toe into the water! There's no time requirement, you can post once today and once this weekend and once next week and you won't be kicked out or anything like that. We've had people leave the project for a months and return to it! Even within a day there's no pressure time-wise. Characters ICly open/close the book as needed, so you'll always be perfectly fine ignoring Twitter when RL things come up.
I love this project because it lets you RP at odd times. Waiting for an appointment? Jump on Twitter for a moment and RP! Slow day at work? There's RP at hand! Downtime between classes? Say hi ICly!
If you have any questions about this at all, please feel free to ask! Either post a comment here or send me a PM, I'll answer as best I can.
Edit: And blind characters aren't excluded. There are magic pens that will write for you if needed. Books can be enchanted to read to you if you can't see. All are welcome! :)
Edit 2: Usually I'm fast to reply to comments and active on Twitter during the day, but tomorrow I'll be in a meeting all day for work. Apologies in advance for delayed reply to LJ comments or anyone's first IC tweets. :)