Sometimes, but not always, I keep separate book records for different editions. This is mostly for paper books though, which just have a 0-byte dummy file.
For fanfiction that had undergone heavy revisions/restructuring, I used to maintain a separate copy of the original version. However, now I just throw the old copy in the extra data files folder, though this means it won't come up in full-text search. (That reminds me of an enhancement request I want to make:
2025228.)