There are dozens of online book clubs worth checking out these days, as it's just not feasible for many people to meet in person every month. Unputdownables has a regular Read-A-Long, for instance, where readers can sign up to follow a weekly schedule of reading (usually) a classic piece of literature. Currently, the group is reading Wuthering Heights.
Slate also has a monthly book club in podcast form, which is a similar idea but not interactive, and The Globe & Mail has an online version where the ongoing comment list provides the discussion for the selected book. At Huffington Post, the book selection has its own subsite with relevant links and articles.
This site was created to give a forum for a group to read and comment on a book but we lived in different places and couldn't meet in person; it has evolved into an open discussion, for people to read or read along, join the discussion or contribute ideas.
Of course, search "book club" in Google Blog Search and you will have myriad options. If you want to rediscover the classics, get into a different genre or just read other opinions about the books you love, there are many, many options online. It is low on commitment and expectation, and you can leave at any time. There is an option for everyone!
1 day ago