I recently read this article, a review of Alan Jacobs' The Book of Common Prayer: A Biography, from over a year ago. The article is written by a person I would consider to be the world's foremost Thomas Cranmer scholar, Ashley Null. Null has earned the right of being called "foremost" both because he studied under Diarmaid MacCulloch, whose landmark biography of Cranmer set the new gold standard, but also because he is doing something no one else has ever done, painstakingly working through and preparing for publishing Cranmer's extensive collection of notebooks called his "great commonplaces." Null has been living in Cranmer's head and heart for quite a while now.
So despite some quibbles and corrections to the review insisted upon by Jacobs, Null's points are worth reading for anyone serious about understanding the original intent of the Book of Common Prayer. I say "serious" because the over four hundred years of Prayer Book study, revision, and historiography has littered the landscape with a lot of erroneous speculation about the theological center (or perceived lack thereof) of the Prayer Book. Cranmer's supposed intent has been coopted to defend practices and doctrine that Cranmer would not have desired. It's one thing to believe that the Anglican tradition should be wide enough to house all the permutations of doctrinal and doxological expression in today's worldwide communion. It's quite another to summon Cranmer for approval. We need more historical clarity.
I would be so bold as to say that Null is in the midst of proving that Cranmer was a convicted Reformational Protestant, not a confused churchman waffling somewhere between Rome and Wittenberg. Even more, Cranmer intended the Prayer Book to be a Protestant and "evangelical" (in the Reformational, not modern, sense of the term) worship document.
Null's article does a good job getting to the heart of the matter, but I commend a search of and appropriation of his extensive writings, including his dissertation turned publication, Thomas Cranmer's Doctrine of Repentance: Renewing the Power to Love.
I leave you with a few of the choice quotes from the article that summarize just what Cranmer was all about with the Book of Common Prayer:
"Cranmer’s prayer books were primarily a missionary means to convert the hearts of English people."
"For Cranmer only divine gracious love—constantly communicated by the Spirit in the regular repetition of Scripture’s promises through Word and Sacrament—could inspire grateful human love, drawing believers toward God, their fellow human beings, and the lifelong pursuit of godliness."
"In short, the heart of Cranmer’s liturgies is moving human affections to serve God and neighbor by the power of the gospel."