I'm sorry I can't specifically recommend it as I don't know which one was her last. But if it follows the pattern of her other novels, it should be a great mystery read.
I'm not entirely sure as I haven't read all of Sue Grafton's works in great detail. But often an author's last novel can be a culmination of their life's work, perhaps tying up loose ends from previous books in the series, or showing a more refined writing style developed over a long career.
The last Sue Grafton novel 'Y' is for Yesterday. In this novel, Kinsey Millhone gets involved in a case that has its roots in the past. There are secrets and lies that she has to untangle. It has the typical elements of a Sue Grafton mystery - a strong female protagonist, a complex plot, and a great sense of the California setting where the stories usually take place.
I would also say 'X Is for X - Rated' is quite well - known, though it's important to note that it doesn't have adult content in a vulgar sense. It's just a creative title within the series, and like the others, it has a great mystery for Kinsey to solve.
The first Sue Grafton novel is 'A Is for Alibi'. It introduced her popular detective character Kinsey Millhone. This novel set the stage for Grafton's alphabet series, where each subsequent book was named after a letter of the alphabet. 'A Is for Alibi' was published in 1982 and quickly gained a following for its engaging mystery plot and well - drawn characters.
Well, 'K Is for Killer' is also a top contender. The story is dark and suspenseful. The way Sue Grafton delved into the psyche of the characters, especially the killer, was really fascinating. It's a page - turner that shows her talent for creating a gripping mystery.