There are lots of hop on hop off trolley tours this one, City View, if you stay on all the way round takes about an hour, and has 9 stops . We just bought the trolley tour at I think $15 each, but this did not included a harbour tour or entrance to any museum , which other tickets did. But it was what we wanted.
The tour guide was a history teacher doing this in the summer holidays, well informed and entertaining. All the major sights were pointed out and a brief history explained. The history of the early revolution, beginnings of the civil war, and British rule were explained.
A good introduction to Boston.