Rihannsu series

Anybody know where I can find Diane Duane’s Rihannsu series in an e-book format?
I’ve checked the publisher and Amazon [and I hate using those guys] and they want to sell me the trade paperback, not the nice, compact e-book that I bought my tablet for.
No, I’m not trying to pirate anything, above board purchasing only…

Not sure if this helps, but four parts are available in the Apple Books app (7.49€ each).

They’re all on Amazon. Search for ‘star trek diane duane’ or the like and they’ll come up. In the US, anyway. Might be different depending on where you live.