I’d have to call ONIX codelists edition 37 (PDF) modest, with (a lucky?) 13 additions and revisions.
Credit where credit’s due: List 17, the Contributor role code, can now specify “Original editor”, i.e. the editor of the first edition who is not an editor of the current edition.
My favorite is on List 65 – Availability. The list mostly covers stock status: out of stock, reprinting, POD-only, that sort of thing. New to codelists 37 is “Not yet available, postponed indefinitely.” This accommodates the intriguing situation where a title has yet to be published… and furthermore has been postponed indefinitely. Are we sure the thing existed other than just a sliver of an idea? You might think to just call the whole thing off, but once in the supply chain, always in the supply chain.
Issue 38 of the codelists is planned for publication in July 2017.