Charles Swindoll has a series of commentaries called "Swindoll's New Testament Insights." In this particular installment, he writes about the book of John.
I love the layout of this particular commentary. Swindoll gives some excellent commentary. I enjoyed the diagrams, especially the opening diagram on pages 12-13 that gives "The Gospel of John at a glance."
Swindoll gives his commentary on each section of scripture followed by an application section. This would be a great resource for those wanting to go to another level in their Bible Study. Swindoll gives great explanation of key Greek words. He also has a section throughout the book entitled "From My Journal" where he gives personal insights.
For those who are leaders, I would recommend using this in addition to other resources that you currently use for sermon/lesson preparation. As with any resource, I would judge it based on your personal theology.