Reformed Episcopal postulants for ordination are told to consult W.H. Griffith Thomas’ Principles of Theology: An Introduction to the Thirty-Nine Articles. It is located here in HTML.
The REC examination also recommends Edward Harold Browne’s An Exposition of the Thirty-Nine Articles, Historical and Doctrinal. It can be found as a free Google eBook here.
I’m delighted that both appear to be solidly evangelical and not at all Anglo-Catholic. Griffith Thomas stresses the common doctrines between the English reformers and the Continental reformers. Some of the best stuff is in footnotes, one of which includes this terrific information:
Cranmer, just before the issue of the revised Second Prayer Book in 1552, and the first appearance of the Articles in 1553, wrote to Calvin (20th March 1332): ‘Our adversaries are now holding their Councils at Trent for the establishment of their errors; and shall we neglect to call together godly synod, for the refutation of error, and for restoring and propagating the truth? They are, as I am informed, making decrees respecting the worship of the host: Wherefore we ought to leave no stone unturned, not only that we may guard others against this idolatry, but also that we may ourselves come to an agreement upon the doctrine of this sacrament’ (Cranmer, Miscellaneous Writings, p. 432 – Parker Soc.).
Griffith Thomas also quotes Nathaniel Dimock in several places. Dimock is the author of Missarum Sacrificia, an exhaustive survey of English divinity, establishing conclusively that transsubstantiation and veneration of the host is alien and repugnant to Anglicanism.
I confess that the REC’s association with the largely Anglo-Catholic APA caused me to worry that it might become squishy on transsubstantiation. I needn’t have worried. The Constitutions and Canons still say (Article 4, section 1) that “Nothing calculated to teach that in the celebration of the Lord’s Supper, the elements of the bread and wine are changed into the natural Flesh and Blood of Christ, shall ever be allowed in the worship or teaching of this Church. Nor shall any practice that teaches or promotes doctrines or practices specifically prohibited by the Thirty-nine Articles of Religion be permitted in this Church.”