This is definitely a first rate translation of Eusebius' work. The work itself is, as most may already know, the first and only surviving one of its kind. In other words, Eusebius' work, as translated here, is the only surviving manuscript of the Church (for the first 300 years).
This text works on several levels. What I mean by this is the fact that a lay person who has never studied Church history could pick this text up and understand it. This is, in large part, due to Williamson's translation and Louth's introduction. However, a seasoned Church historian would also benefit from this translation and work due to its clarity, and the fact that the sections are kept short and concise leaving the reader and researcher with nice 'bite' size chunks to digest.
This is a 'must read' text for anyone interested in the first 300 years of the Christian Church. Eusebius gives details of events, names, places, doctrine, issues, etc. that helped to shape the Christian Church. Events such as the persecutions of Christians under Nero to Marcus Aurelius are detailed. Genealogies of Bishops since Peter to Eusebius' day are detailed and listed, as well as certain heresies and councils. And many other extremely pertinent details (such as doctrinal disputes, etc) are included in this work.
If you are wanting a detailed account of the first three hundred years (the early Patristic Period) of the Christian Church, then you will not want to be without this text (esp. due to William's great translation and revision work). I highly recommend this book!