Quite frankly the best book I have ever read on the subject of fellowship within the church. It is packed with biblical truth and has a pastoral wisdom that should shape any work on the subject. Some may not consider this a scholarly work on the subject. But Milne knows his stuff and typically refers to "scholarly things" when need be. In other words, he's not writing to prove to us that he is smart. He is writing to change us. Something, sadly, most "scholarly" works really fail to do.
An obscure, hard to find book, but one of the best books I have read on the subject.
The book is practical theology. It is simultaneously theological and exegetical with a direct eye towards intensely practical issues. Milne's diagnosis of issues, etc is so apt that it is apparent he is not a mere academic but a real practitioner. However, this in no way diminishes is exegetical and theological capabilities.
If this book were more readily available, I would prescribe it to anyone desiring to read on this topic.