Karen McManus’s books are murder mysteries aimed at young teenagers and appeal to 12-15 year olds (approximately). On her website Karen McManus describes herself as a writer of “twisty YA thrillers”, which is a nice way of putting it. Her books certainly go down well with their target audience. One of Us is Lying is the first in the series. One of Us is Next is the sequel to One of Us is Next, and so needs to be read after. Two Can Keep a Secret and The Cousins are standalone books so don’t need to be read in any particular order.