While wrestling with Python's shelve module, I ran across ACID. Interesting thoughts.
Plus what appears to be the related Tumblr blog: python sweetness. Also interesting.
Not sure I can make heavy use of it right now, but it's helpful to see the thought process.
I find the subject of shelve (or pickle) and schema change endlessly fascinating. I have no good ideas to contribute, but it helps to read about ways to track schema evolution against data that's as highly class-specific as shelve data is.
Versioning class definitions and doing data migration to upgrade a database is -- right now -- a fascinating problem.