This was a very good expositional commentary on the Gospel of Mark.
A number of years ago the Christian Union I was involved with in Cork were involved in IFES Ireland's Free Gospel Project, which was based around the Gospel of Mark.
We did Bible studies for Christians (one on each chapter) and also for seekers (not one on each chapter).
In all that time the idea that Mark may have been writing to let us know what it means to be a disciple was never discussed. We struggled with why Jesus had people remain silent and, at random times, such as with Legion, He allows people to tell of Him.
This commentary, and Donald English of course, hit the nail on the head when he discusses the different reasons Jesus allowed Himself to be fully revealed.
I think this is a wonderful commentary, and besides for chapter 8 being covered a little sparsely, which is surprising considering a lot of what English draws from the text is what it would mean for disciples in Jesus' day, Mark's day and our day. That chapter has Peter reveal Jesus as the Christ and Jesus first speak of His suffering and tells others to follow Him they have to take up their cross.
Discipleship as one of the key elements in Mark is just inspired.