Framing the Middle Ages and The Inheritance of Rome both look to cover similar subject matter. Is the latter an update and improvement on the former? Or a condensation of it (it's shorter despite covering a sllomewhat longer period). I want to read his take on the period but am unsure which to purchase.
Is the latter an update and improvement on the former?
In very short answer, while the former is rather highly academic, the latter is written for wider audiences including lay historians (it is also one of the series of Penguin History of Europe).
If you wish to read and consider various topics of EME in more depth, you should probably go with the former (on the other hand, if it is your first time for Wickham and unless you are generally graduate level or specialized in medieval history, I'd rather avoid to recommend the former strongly).
Though I generally prefer Inheritance of Rome for EME proper, Wickham also writes the third major alternative, Medieval Europe (2016).