Having been a fan of the Wardstone series since they were first published, and having read all of them, I was eagerly waiting for the publication of A NEW DARKNESS. However, with 13 books before this one, I did wonder how successful the new book would be. I shouldn't have worried.
Although you don't necessarily have to read the previous books before reading A NEW DARKNESS, you will possibly enjoy it more if you have read them. A lot of the characters that appear, or are referred to, in this new book also appear in the previous work. This means that in order to fully understand relationships and previous battles, you need to have read the other books. However, for someone staring with this new series, Delaney provides enough information to explain relationships and conflicts on a surface level. As the title suggests, there is also a new threat to the County that Tom, as the Spook, has to face.
For anyone who has not read books by Delaney before, Tom Ward is a Spook. This means that he is paid by people to get rid of ghosts, ghasts, witches and boggarts. He is their defence against the dark. Tom's world is not all about clthearly defined good and bad though. Some of Delaney's characters manage to blur these boundaries, making you question who is friend, foe or a mixture of both. Despite being for younger readers, they are incredibly intelligently written, taking many themes into account.
If you have not read any books by Delaney before, I would strongly recommend you starting right at the beginning, THE SPOOK'S APPRENTICE. However, you can easily start here and enjoy it without needing to visit those previous works.