It's always a bit tough to tell (since I can't un-know things when I read them), but at the very least, this book is chock full of spoilers for the previous ones. What I don't know is how accessible the characters are for someone who hasn't read them, but it feels like there's an assumption that people have knowledge about them.

FWIW, the series reads very quickly, so it might be worth grabbing the first book to see if you like the writing style.