I'm convinced we benefit by re-using the CPython guide, but the idea was to track change by pulling in CPython changes as we go along. In practice, this doesn't happen, and when a backlog has built up, the merge looks scary.

Chapters are files. There are three cases to consider:

1. A file is the same in Jython as in CPython (yay!).
2. A file has a small number of differences in Jython's copy from CPython's. One might be able to have a file of the same name and merge the changes.
3. A file differs a lot. Jython needs its own version entirely. (Include here chapters we drop and chapters we add.)

In practice, 2. is where the problem lies, as it's always more important to make a specific change than keep up.