There could never be a better translation and publication of Pepys' wonderful diary. Lanthem and Matthews have put a lot of time into translating this series.
In the first book there is an introduction of several essays - a short biographical piece and information on the use the diary has for both literature and history, as well as a history of previous publications of the diary. These come in very useful and are also extremly interesting foreground reading before beginning the actual diary itself.
The editors explain how they have translated the diaries and the difficulties and have tried to present the diary how Pepys' would have wanted it. They have tried to make it authentic as possible - only changing bits they absolutely have to and the reader is always informed of such changes.
Pepys is an extremly important part of English history as he was witness to the restoration of the king after the death of Cromwell as well as the plague and the fire of London. His diary is wider then that - it is a record of humanity. It is unique in that it is very honest - a graphic detailed account on a man's life both public and private.
Such history from a first hand account and not regergitated by modern day historians is invaluable for anyone interested in the history during this period.