While listening to Harry Stebbings interview Boris Wertz on the 20 Minute VC, I heard Boris refer to his free ebook A Guide To Marketplaces. So I read it.
It was a quick read, but very useful for anyone who is interested in marketplaces. Boris lays out all the terminology, explains different types of marketplaces, dynamics of building a marketplace, and metrics you should pay attention to.
If you are building or investing in marketplaces, make sure you grab a copy and read it.