The role of the `Six Preacher' was one entirely unique to Canterbury. Created by Archbishop Thomas Cranmer in 1541, the new role was just that: six preachers to be appointed for the purpose of spreading the word of God, in plain English, directly to the people, very much in the spirit of the new Protestant church.
This book was painstakingly researched, and beautifully written, by Derek Ingram Hill, himself a `Six Preacher', as well as being a Canon Residentiary and also parish priest. He was therefore well qualified to take on the task of cataloguing every `Six Preacher' to have been appointed from the beginning, and taking it right up to 1982, when this book was published.
However, this is far more than just a dry list of names. Canon Ingram Hill also included interesting details and character traits of the men involved, where this information could be gleaned from the archives. For example, we learn that the ultra Puritan, Richard Culmer, delighted in smashing the `Popish' stained-glass windows in the Cathedral. We also read about the early 19th century, Allen Fielding, who spoke so slowly that he became known as "the minute gun".
As to why the role of `Six Preacher' is unique to Canterbury, there is much speculation, and it could be that Cranmer introduced the role as a counterbalance to the new `Dean and Chapter at Canterbury, which contained a number of people re-employed from the old monastic days of Christ Church Priority.
The role of the `Six Preacher' continues today; in fact, the position has remained unbroken since 1541. During the Commonwealth period, when the Dean and Chapter at Canterbury was abolished, the position of `Six Preacher' was the only one allowed to remain, proving this to be, not only a unique, but also a somewhat resilient role.