This month is a pair of of books from an excellent coach with a career of experience coaching high school and college football. Coach Gordon's first book "Coaching the Under Front Defense" outlines how the front aligns and functions.
His 2nd book is a all about "Split Field Coverages". The book covers a fully developed coverage package.
Both books are great reads. If you are a new coach looking to learn about under front or split field coverages these books are a great place to learn. If you're already experienced coaching these concepts this is a great chance to see a successful defensive coach's explination, progression, and coaching points. I took a bunch notes on details from Coach Gordon that I've added/I'm adding to our progression.
Not convinced? Listen to Coach Gordon on the Deep Dive on Defense pod cast. Listen for the split field coverage info and killer Boston accent.