Heretic's Creed is the fourteenth Ursula Buckley title by Fiona Buckley. It has dropped in price (various prices, some better than others) in the US and UK. Still a bit pricey, but most of the later books in this series don't go on sale very often, and are very pricey when not on sale, so...
And also, this is one of my very favorite series.
Kindle US, $6.49, pretty expensive still - buy at Kobo with coupon if you can:
https://www.amazon.com/dp/B01M5FQOOZ
Kobo US, $6.99, but if you use "Partners22" for 40% off, and if you have the VIP discount, it can be as low as $3.39:
https://www.kobo.com/us/en/ebook/heretic-s-creed-the-1
Kindle UK, £3.99:
https://www.amazon.co.uk/dp/B01M5FQOOZ