I just pulled Object-oriented Programming in R from Leanpub, Gumroad and iBooks and enrolled it in Kindle Select. Will see how it performs compared to Meta-programming in R so I have some comparison.
I’m thinking of moving my books exclusively to Amazon and enrolling them in Kindle Select. I’m not really selling anything in iBooks, I haven’t sold anything at all on Gumroad, and while I do sell a bit on Leanpub, I don’t plan on putting future books there after they made the $99 + VAT fee for them. With Kindle Select, that requires exclusive sales on Amazon, I can make promotions and such, so it is a better choice, I think.
It does mean that I can only sell in the Kindle format—which annoys me a little since it doesn’t support math and doesn’t have the layout I can make with PDFs—but I can make paperbacks to compensate.
Anyway, if you want a PDF or EPUB version, get my books now, because later today I am moving them to Amazon exclusively.