OK, this is my opinion. I get all my quilting books hard copy. I've gotten a couple ebooks and even though you can look at them on your PC with the free kindle app, I still find them difficult to use. I have a kindle & Ipad too, which are way too small for me to see any detail. I also had the unfortunate experience of getting a Kindle version of one title that was B&W and couldn't see any of the detail in the color diagrams, so had to rebuy the hardcopy version.
I love Harriet Hargrave's Quilter's Academy, but they are on piecing, not long arm quilting.
For long arm I like Quilting inside the lines by Pam Clarke and Pathways to better quilting by Sally Terry. And, even though I don't like ebooks, I do like youtube long arm quilting videos!