I buy ebooks straight from publishers like Nostarch and Leanpub. (In fact, I have an older edition of this book). There are a few books that are sold directly by the authors too. All of them DRM-free.

I actively avoid publishers and sellers who don't respect me as a consumer/reader. People need to start demanding better deals, or else we'll end up with monopolies that won't think twice about deleting books in your custody that you purchased from them.

Got any notable suggestions from Leanpub?

Yarr, that do be a problem matie.

In all seriousness, how has DRM not yet been recognized as the failure it is?