Touring Rome's Centro Storico

Sherpa Alison will be leading a more intense tour this year, now we're (she's) got a clearer idea of where things are. We'll be spending at least two days visiting sites related to David Hewson's books. Our first visit amazed us by the proximity of the churches, palaces and villas mentioned in the books, but they were often found unexpectedly; we'd look up from the map expecting to be somewhere else, but THERE WE WERE! Can anyone suggest a sensible route, taking in all the sites? Would anyone like to join us?