I was firmly in the camp of those who despised everything Constantine and saw him as a monster who was used by Satan to creep into the lukewarm Church of the 4th century and corrupt her. This then (supposedly) left no room for the true "Kingdom Christians", and so they were either forced out or left of their own accord to start the "Pilgrim Church", an extreme Protestant ecclesiology which E. H. Broadbent (of Plymouth Brethren persuasion) popularized in his book PILGRIM CHURCH HB
I have been on a long spiritual journey and there have been many difficult questions to answer along the way, and some answers I am either not totally comfortable with or have not found yet. One of those answers has been Constantine's role in the Church. There can be no doubt that his role in the Church did more to alter her course perhaps more than at any other time in history. Perhaps only Luther would come close in the effect one man has had on the course of Christian history. The split between East and West during the Great Schism in 1054 was devastaing too, but no one single person can pinpointed there. What has divided Christian thought through the years has been what exactly Constantine did, and why. What were his motives? One book I have but I have not yet read is called The Anatomy of a Hybrid by Leonard Verduin. This book sets out to completely villainize Constantine, refers to the Church after him as the "Constantinian Hybrid" and is being made increasingly popular by other authors such as David Bercot, author of Will the Real Heretics Please Stand Up: A New Look at Today's Evangelical Church in the Light of Early Christianity and Will the Theologians Please Sit Down, and Church groups such as the Anabaptists, Baptists, Plymouth Brethren and just about every independent Protestant denomination out there, plus perhaps a few pre-Protestant groups such as the Moravians and the Waldensians.
Now, our author is not part of any of the ancient Churches (Roman Catholic, Eastern Orthodox, Oriental Orthodox, Nestorian etc.), but does hold to the Church model we find there. I assume he is a Presbyterian as they are classicly the closest to the ancient Churches in theology (also the Lutherans) out of the Reformed or Protestant camps.
The book itself is quite big, and least 25% longer and wider than an average paperback and it is also over 370 pages long making this a big book. So while I paid for it, I at least feel I'm getting my money's worth.
Once I read it I will give my own verdict and fill you in on the details if you have not read before then.
References to the above books are not necessarily endorsements on my part; they only show the progression of thought from point of view to another that I have had.