The fact that J.K. Rowling is not on this list is because the fact that I adore her is so implicit, it's not even a question.
I have read and loved every single one of Charles Todd's novels. Considering there's been over 20 books, that's no mean feat.
Beautiful writing, only one dud so far (and even that deserves a reread).
Auto-buy. The only dud has been Gameboard of the X. Let's just forget that book ever existed.
Juliet Marillier writes fantasy so beautifully. I love her YA series and her shorter series. Interestingly enough, her most famous series, Sevenwaters, was the only one I didn't care for. Everything else has been brilliant.