A foreign country
The guide rather than just presenting you with lists of dry facts turns your average history book on its head, it presents historical fact in the same readable fashion that an historical novel would present it. So, for example, the book opens with your arrival at the gates of medieval Exeter. You are stunned by the new buildings, knocked out by the stench, and, as ever, the children are eager to find out who you are, and where you're from.
The chapters are set out much as your average guidebook would be laid out. There are chapters on language (did you know that William Caxton wrote and published a French / English phrasebook?), how to find a bed for the night, and the best place to stay, manners and medieval humour, what jobs are available, where to find a doctor (and why you might be better advised not to do so), what to eat, and what to do in your spare time.
Concentrating primarily on the fourteenth century but also drawing on some sources from outside the period, this is both fascinating and eminently readable - a sort of Horrible Histories for adults. It's great fun, but there is also a serious side. It's impossible not to be moved by Mortimer's accounts of the Great Plague. And this is largely due to his writing style, moving away from the bare facts into the humanity is compelling. Who could not feel for the man who had buried his five sons by himself with no bells to mark their passing, or service held for them?
You inevitably find yourself wondering how you would have fitted in to this period of British history. As a musician, if I was lucky I would have apparently earned a good wage, but as an eczema sufferer I might have been diagnosed with leprosy and forced to wander through the land with no community to call my own. As a woman, I would have run the lottery of childbirth - a 1 in 50 chance of dying per birth, and could be forced into marriage against my will. But as long as I was literate and born into an upwardly mobile family, perhaps a merchant's family, there would be the chance to read some seriously good literature from Chaucer to the writer of the wonderful Pearl, and of course John Langland. There was great music, free street theatre, pretty good food in years of plenty, and the chance to go on pilgrimage.
The past is indeed a foreign country. If you want to read a definitive guide book to it, it should be this one.