Hello LW,
I am mremre, friend at university reccomended me hpmor some time ago and I really liked it. I briefly skimmed through forum when my search for music textbook broght me here and got interested enough to sign up. I study mathematics, among my other interests are: go, music, AI.
Sad to see that ebook version is DRM protected. On your website you list far less retailers than Hatchette does.