I've noticed over time that Helen Harper is really good at putting the first book in a series free for a while, but I don't see many (any?) of the rest of the books in her series go on sale. But, luckily, they are KU, and I have that, so I don't get stranded...
And, right now, that's the case with
Box of Frogs, which is the first in Harper's Fractured Faery series - it's free, and the rest are KU. And I really liked her Slouch Witch series, and also a couple of other series, so I'll give this one a try.
Kindle US:
https://www.amazon.com/dp/B07C26QFHM
Kindle UK:
https://www.amazon.co.uk/dp/B07C26QFHM