Buy every one you can afford, you won't regret it. If a gun you want to build is in 'Art and Evolution of the Longrifle' on the KRF site, get it, it's that good. The individual school books are great too, it you can find them, anything by Whisker. I've got the Maryland, Bedford and York books and pick them up at least once a week to dream and plan! Books never get out of style or lose value...