I think this is a good idea and I anticipate that it would significantly help me, for one, with reading the Sequences. I do however see a potential problem with implementation:
I would recommend one new post per day, going in order of the book. I recommend re-posting the entire article to LW, including any edits or additions that are new in the book.
That would be a lot of posts. If we're talking about making a new post in Discussion everyday, that would likely drown-out most other threads. It would be even worse in Main. (ETA: I think I should have written "dilute" instead of "drown-out." Going by a rough estimate of the current rate of Discussion posts, the proposed series would probably make up only a quarter of Discussion, though that's still a significant change.)
I could, of course, be misunderstanding something, in which case I apologize.
[edited iteratively]
I don't see a dilution of that magnitude as a problem when the material is the core material of the site. It wouldn't be obviously silly to have this as a lasting feature of the site, and start again when we finally finish.
The book version of the Sequences is supposed to be published in the next month or two, if I understand correctly. I would really enjoy an online reading group to go through the book together.
Reasons for a reading group: