A nice idea, poorly executed.
There are a few things in here which should be great. Alchemical recipes, firearm rules, new classes including the barber-surgeon, a lengthy description of the town of Bury St Edmunds. But they are poorly thought out and lack substance. The book as a whole lacks any focus, skimming across the surface of the original and suggesting rules tweaks which lack any real depth or insight - your own house rules are probably better already. And the town of Bury St Edmunds reads like a shopping list instead of a tapestry.
In addition, the writing is poor and so is the artwork, making it difficult to get a sense of immersion in the setting that the original game does so well.
If you don't have the original game, buy it!!! But avoid this sub-standard addendum.