As I can't propose them, I'll request them here.

It'd be nice to have a way to indicate the type for at least some of the common spoken work forms. There's currently no work type which would apply to these. I'd suggest adding:

• essay (e.g. an essay contained within ('part of') an AudioBook of a collection of essays)
• short story (e.g. a story contained within ('part of') an AudioBook of a collection of short stories) (ex: http://musicbrainz.org/work/17bbb31f-4c23-4534-bf3e-d57be49ca195 )
• book (e.g. AudioBooks)

Note: the list also included Poem, which has been added.