Isserley is small, and has very thick corrective glasses. She has severe pain, and sleeps uncomfortably and fitfully. She loves taking long, extended baths. She cannot eat most food. She spends most of her time driving around the scottish highways, picking up lonely male hitch-hikers, which is easy for her to do. This is because she has a very large pair of artificial breasts, which she flants in low-cut tops.
Once she picks up the hitch-hikers, she tries to ascertain whether they will be missed. Once she has convinced that they would not, they are suitable for her purpose. The purpose is immaterial, because the story is about Isserley, about what it means to be human, what identity is and what morality is. Ultimately, the things that really matter are, for all intents and purposes, Under the Skin.
I have tried to not drop any spoilers here. Everytime the reader processes what they have read and tries to predict where the story is headed, it veers sharply away. Equal parts creepy, horrific, sympathetic and amusing, the book is a slow burn must read.