This entry comes from the comment section of my last entry. I thought I'd open this up for more discussion, if anyone is game.
Three reasons why you should discard your copy of Dom Gregory Dix's The Shape of the Liturgy, if you haven't already:
1. Dix's whole 4-fold shape of the liturgy thesis is contrived on his own speculation, with absolutely no historical verification or support (read none). As a result, those contemporary rites that are based on Dix's thesis are built around an artificial construct.
2. Anything of actual historical significance in the book can be obtained from better and more up to date works. So STL is utterly obsolete as an authority in liturgical studies, despite the opinions of a number of antiquarians and liturgical wannabes who still treat the book as if it were the most important liturgical resource ever written.
3. Dix never understood Cranmer's theology, but presented himself authoritatively as if he did. The resulting damage done to Cranmer studies and studies on the Anglican liturgy will take generations to undo (if ever).
Those are three reasons off the top of my head.