While I would say that the notion of a "Protestant ecclesiology" seems a bit of an oxymoron, what little understanding of the church I got from an Evangelical seminary and the PCA (and even Anglicanism) does not even come close to what de Lubac provides here. De Lubac's style is surprisingly informal but heavily footnoted with Scriptural and Patristic sources and deceptively dense. My love and understanding of the Church in all Her "splendor" has increased by reading this master of theology. If you love the Church, read this, and you will love Her more. If you are Protestant and love the church, read this, and you will see what that love should mean.
The section on the Church and the Blessed Mother is the best (its at the end) but only by a small margin. Im getting tired of having to always gush about de Lubac, but his books are outstanding.