A thread for each book, with a first post updated with the current errata ever so often, would get a hearty recommendation from me. It's a nicely organized way to do it, and it makes it very easy to find the most up to date information. A few different game forums I frequent use that (Battletech among them), with the usual format of product, page number, issue noted (without long arguments ideally), and suggested corrections (if necessary). I'd think that would be a solid format to follow, provided (and this is really key), clear examples for the desired format of errata submissions are provided at the beginning. Without those examples, confusion can easily result.