Honestly, tracking down 'Unwanted Luna' was its own little saga for me. I first stumbled on the ebook through Kindle Unlimited—it was free with my subscription, which was a nice surprise. I think most of the early chapters are still up on some of the bigger novel serialization sites, but the official, complete version is definitely on Amazon. For the audiobook, that's trickier. I ended up going with Audible; they had it narrated by someone with a really distinct voice that actually suited the main character's internal monologue quite well.
I tried a few other places first. I remember Scribd had it listed, but it wasn't part of their subscription library at the time, so I'd have had to pay the full price. Apple Books had it too, but the sync between my Kindle and the Audible app is just too convenient for me to switch. Sometimes these paranormal romance titles get exclusive deals with certain platforms, so if you're not seeing it in one store, it's worth checking a couple others. My sister actually found the ebook bundle with a prequel on the author's personal website, but that was a limited-time thing.
One thing I'd caution—I saw a ton of 'free pdf download' links on random forums that looked super sketchy. The cover art was always slightly off, and the formatting was a mess. It's worth sticking to the official retailers just to make sure you're getting the proper edition, especially since some of these indie authors do release revised versions later.