The Hidden Life of Prayer

Along the lines of Garrett's post, Grudem also mentioned the book he rereads the most is The Hidden Life of Prayer by David M'Intyre. This is arguably one of the best books in the devotional trajectory that has ever been written. You may find the book online here. The problem with this format is the location of the footnotes. The footnotes are actually just as good (if not better) than the whole book! In the original printed versions, the footnotes were located on the page of their citation (some of the subsequent reprints also have them in the back). A person reading the book would miss out on a great deal of the glory of this little book if they don't read these footnotes.