I'm working my way through the Greystone series by Margaret Peterson Haddix. It's a trilogy so far - I'm not sure if there's more to come or if it stops at number 3. It's a children's and young adult series, but I can attest it's also a good choice for adults. This is because it's a science fiction series which has well-thought-out world building which everyone can appreciate, young and old.
The first book of the series is The Strangers. It was available through my public library's ebook system, although of course it might be available in print there also. I read the first one and got hooked. The third one so far is really great and introduces some additional characters. I'm still reading that one, so I can't comment too much at this point, but that's probably a good thing as I don't want to inadvertently give away the plot.
The author Margaret Peterson Haddix is one of my favorites for her gripping plots and relatable characters.