Blues Harmonica Method
Availability of your books to purchase in my area pushed me towards the two volume Classic Chicago Blues Harp set. Subsequently I was able to purchase some of your more recent books to supplement these. Very happy with all of them. Though I'm likely to be an on and off member of this site I find books work really well for me so mixing the two together is my preferred self teaching approach. Just wish I could find someone locally to work with in person!
So the question concerns tongue blocking. It looks to me as if your teaching approach used to introduce tongue blocking later than you do today. The two School Of Blues Method books seem to indicate that tongue blocking is now introduced right at the beginning. No issue for me as I work on both embouchures every day with the ultimate goal of being mostly a tongue blocker. Are these two books different enough in approach to make their acquisition important? Perhaps an obvious yes answer but is the material a new approach?
Yes, that's correct, I teach tongue blocking as the primary embouchure now. Yes, keep working on both, it's a good skill set to have. The School of the Blues Lesson Series method books are not a lot different from the Harmonica Masterclass ones, so I don't think you need to get those, except for Improving Blues Harmonica, Blues Harmonica Accompaniment Playing and Rock Harmonica... which are in my opinion some of my very best books.