A shepherds look at psalm 23

This book was written in the 1970's or some where around there. I've read it several times over the years, but most recently, this past week.
The writer, Phillip Keller, had at one time been a shepherd. The book was written to detail what the psalmist David was thinking about as he penned this particular poem. Phillip wrote the book to describe for us today who have no knowledge of being a shepherd what someone from that time did for the flock which is under their care. He takes each line of the psalm and describes what the dilligent shepherd had been doing for the sheep under his care. It is only around 122 pages, but is filled with good thoughts about what God has done for every person on the planet Earth, since we are likened to sheep in the Bible. God cares for us all and will spare no amount of pain and trouble to help us.