As far as I know, Trek books aren't available DRM-free anywhere.
Very true. Star Trek eBooks are only sold with DRM.
Ah! That explains my troubles
Well, in the end, I just got 'Resistance' using my Kindle app for iPhone. I realized that, while I disapprove of DRM, the primary reason I do so is that I feel like I don't really own
my books, and that as soon as that DRM goes out of fashion (as they invariably do), the books I've purchased under that DRM regime will all be lost. However then I realized that I don't really hold on to my Trek books anyway- they usually join a giant pile of books that eventually ends up with the Salvation Army. So since I'm not really interesting in 're-reading' my Trek fiction, it's not as bad to purchase it with DRM and then just let it go once I'm finished.
As it was the buying process was really painless and I am now enjoying Resistance on the kindle app.