I would read everything from this author. Philip Keller presents spiritual truths with charm, humor and insight into us as the Lord's sheep. Excellent! Also highly recommend A Shepherd Looks at Psalm 23 which we used in a fellowship group. I plan to share Sheep Dog with family.
Please continue to publish Lessons from a Sheep Dog and A Shepherd Looks at Psalm 23 by Phillip Keller. In my judgment they are a must read, not only for Christians, but also as an evangelistic outreach.