Church Times 'Best Christian Books'

So I am told, as a Church Times reviewer, that they're doing a feature this autumn on 'the best 100 Christian books of all time'. And they want suggestions. The criteria are:

Works should be of enduring value, influential in their time or after it. The list will encompass fiction and nonfiction, theological scholarship and popular titles, authors ranging from St. Augustine to Eamon Duffy to C. S. Lewis. (The only suggestion we will not consider is the Bible, divinely inspired authorship constituting an unfair advantage.) Among the categories to consider: mission and ministry, church history, theology, prayer and spirituality, the Old and New Testaments, liturgy and worship, literature and apologetics.

Now, there's a fun parlour game! What to nominate? I passed over the Prayer Book (which won't be short of friends) and Pilgrim's Progress (likewise). Here is my initial suggestion and rationale:

Philip Jacob Spener's Pia Desideria (1675). It's a short call to arms - or rather, to renewed piety: it was the book which kick-started Pietism, and is therefore indirectly (no, actually, pretty directly) responsible for modern Evangelicalism. What makes it so wonderful is that it combines two things which are almost never brought together. First, a moving call for moral and spiritual renewal: its insistence (which both Pietists and Evangelicals have too often forgotten) that to be a Christian means to follow Christ, not to be able to win doctrinal arguments. Against the hair-splitters and heresy hunters of his day, he warned that at the last judgement ‘we shall not be asked how learned we were’, but rather ‘how faithfully and with how childlike a heart we sought to further the kingdom of God’. And he added that if St. Paul were to try to follow one of the theological debates of the age, he would ‘understand only a little of what our slippery geniuses sometimes say’. BUT, he combines this preacherly idealism with a level-headed practicality about what should be done. In particular, he makes the revolutionary suggestion that Christians should not leave their spiritual fate in the hands of their ministers, nor of the political powers who usually dominated their churches, but rather take matters into their own hands. He recommended ‘the ancient and apostolic kind of church meetings’, that is, Bible study and discussion groups for mutual support and encouragement. Methodist bands and classes got the idea directly from him. It seems so normal now that it's hard to grasp how empowering and revolutionary it once was.

I think Spener deserves top-100 billing. But maybe just because I've been working on it these last couple of months. What other obscure gems want rescuing?