I must go on record as saying anything that has Al or Gretchen's name on it is more than worth the $$. Some years ago I wanted to see if Rotary tying was for me? Purchased a Dan vise. Because I am an old guy and set in my ways it would not have been possible for me to adapt. (I am quite hard headed as those that know me will readily agree with)
I purchased almost all of their tying VCRs for Liz when she wanted to improve her tying.
Every now and then I go back and look for some tip I remember I had picked up from them.
They are without a doubt the best instructors of fly tying in the World. Always ready and willing to help even dummys like me.

Book or DVD? A no brainer for sure. BOTH!

Denny 64 years of tying and still learnin.