Most of my books are bought at charity shops, for various reasons. It is easier to find English books in thrift stores than in physical bookstores; the books are really cheap; it keeps existing books in circulation and is better for the environment. The downside is that I am confined to whatever people donate, but I have found some of my favourite authors that way. If I do find an author I really like, I often purchase more of their books – sometimes on Amazon, sometimes ofrom a local secondhand bookseller (online).
This one was a lovely surprise. I read The Hostage a month or so ago, but this one is way better and I am really enjoying it. I did not enjoy The Hostage enough to stock up on Mackintosh’s books, but this one may convince me otherwise.

I Let You Go and I See You are extremely good too.
Thank you so much for the tips. I am always looking for recommendations!
This looks like it may be a series of books and might even be made into a tv show (ala Columbo, Elsbeth, and others.