Hello all, I thought I would check in again and report my findings on this.
Although tomswift2002 helpfully pointed out that rakuten kobo store does indeed have the Prometheus trilogy available, the copies they sell are unfortunately saddled with Adobe DRM. This, I have surmised, is due to their unusual situation being from published by Titan (under Titan Books imprint) rather than Pocket Books.
This a problem for me, because I do not pay for DRM-hampered media as a matter of personal principle (and also as an investment against future inconvenience).
Now, it seems that at some point Simon and Schuster made the (commendable and delightful) decision to offer their entire Star Trek book catalog, both backlog and new releases moving forward, in a DRM-free epub format when purchased through startrekbooks.com or online ebook retailers such as rakuten kobo. I was able to dig up an announcement from an earlier trekbbs thread explaining Star Trek Pocket Books releases being DRM-Free: this:
http://news.simonandschuster.com/pub/sf/ResponseForm?_ri_=X0Gzc2X=YQpglLjHJlTQGmeobt4wh9szdUrrzbFAzb0za0yjoFAtOJXEs3Hkai81IDzcThhbVXMtX=YQpglLjHJlTQGonUU64ezfFzdrapzbFzen1Jd4SKFvHorzfyBqDgOzfcrruUwm8sO&_ei_=EuMjGFYTeYQXDXwLPD50GDkNlWGJjQ1O7eIC8hHpWXLNfVNEV306Criu2ZfM1e2jqA_dAmK5B17z9CNC4H88xrV--8s
Titan obviously does not follow the same policy with Prometheus trilogy. It is frustrating to own the books in paper and not be able to purchase DRM-free electronic versions of the text (I am also unwilling to pirate the books, for ethical reasons). Ultimately, I was not able to locate any DRM-free version of this trilogy available at retail, nor do I possess the necessary knowledge and/or tools at present to be able to remove the Adobe DRM infection from the books were I to purchase them. I was just about ready to give up and read paper...
However, in the end I
was able to achieve my goal of getting to read the trilogy on my device,
without breaking any laws or licensing, and also
without paying money for a crappy DRM-saddled copy of the book

Here's how I did it.
Probably this is old news to many ebook enthusiasts, but it was news to me and it made my day. I was able to create an online account with my public library card (in my case, City of Toronto Public Library), and then "check out/borrow" the ebook directly on my kobo device. On a Kobo, the library service connection is handled through a menu option titled "Rakuten OverDrive." It all worked perfectly without any headache and I now have the first Prometheus book to read totally free of charge (not counting my property tax contribution to the public library, I suppose), and it appears to be available on my device like any other ebook, saying it is"available until October 25th," whereupon I expect the library loan will expire and the book will be checked back into the library for someone else to borrow. I expect it will also return to the library once I have finished with it at some point before that date.
The public library has the entire Prometheus trilogy, and there isn't even a waiting list to borrow them. They have a large selection of Star Trek books, in fact. Rakuten Overdrive apparently has this program set up with a "thousands of public library systems worldwide," according to their website. It is evidently totally legal and properly licensed and I am very happy to learn about this as it will enable me to enjoy digital versions of many books I would otherwise have had to carry in paper format.
I hope this proves helpful to you, if you live in a municipality with a public library system see if they have OverDrive. I would expect Kindle must have some equivalent program too but I haven't looked into it.