Killing Cupid / Louise Voss and Mark Edwards.

Alex Parkinson is in love with his writing tutor, Siobhan. He has never loved anyone like this, but how can he convince Siobhan that they are meant to be together? So Alex stalks her on Facebook and finds out where she lives, buys her presents using her own credit card and sends her messages telling her exactly what he wants to do to her. He breaks into her house, reads her diary and secretly listens to her while she takes a bath. Isn't that what all lovers do? But when a love rival appears on the scene, Alex has to take drastic action, and soon a young woman lies dead after tumbling from the roof of her house. Now there is no-one standing in the way of Alex and his true love. But someone is watching Alex too and he is about to discover that there is a thin line between love - and hate.