From my perspective, the best English prayer book ever proposed was 1923. It should be the proper basis upon which any future revision should emerge.
This book is the initial draft of the ill-fated 1928 Prayer Book of the Church of England. It is the result of a long process extending back 20 years to revise the 1662 Book of Common Prayer. Initially the revision was only to concern rubrics, so as to reduce tensions between the Evangelical and Anglo-Catholic parties of the Church which had, on occasion, resulted in embarrassing trials in secular courts. However, the enormous social upheaval caused by the Great War (World War I) brought about demands for greater changes, both in language and theology. These were largely voiced by Anglo-Catholic clergy who had served as chaplains in the war and in urban slum parishes, and found that the lay-people they encountered had great difficulty relating to the 1662 BCP, and that it had significant limitations. This book was the initial result, and, unfortunately, it largely ignored those who initially fought for changes. This draft resulted in responses for further changes by certain groups: a "Green Book" from strong Anglo-Catholics, an "Orange Book" from moderate Anglo-Catholics, and a "Grey Book" from a more liberal group. Note that Evangelicals had no response; they generally preferred no change in the 1662 book.
I would have said "fortunately, it largely ignored" the revisionists: twenty plus years of work and down the drain it went. I don't believe any of the alternative books contain much of enduring value.
However, the 1928 deposited book is available now in print once again.
What this volume has that no other does is all the new Lessons for Mattins and Evensong. It means, of course, that the 699 pages of the Prayer Book are supplemented with an additional 1129 pages of Lessons (plus Tables). As others have noted, it is questionable whether the modern binding supplied will hold up under this immense weight. It possesses only a single ribbon for marking one's place. But, nonetheless, there it is.