A ReadUp is a social reading experience. Think of it as meeting up inside a book.
ReadUps offers a web-based reading system that works on tablets and laptops. With it, you invite friends to read with you for a limited amount of time. In addition, you can share comments on any paragraph, or message the other readers in real time. All you need to do is give people the URL for your ReadUp and you're good to go! To slap a password on the ReadUp (so only the people you share the password with can get in), buy a $5 upgrade.
When the allotted time runs out, the ReadUp disappears.