To begin with, both the leads killed the movie. It mainly starts with Maren biting a finger at a friends sleepover where it leads to them switching places. Her dad leaves her, just as soon as she is 18, then gradually Maren meets Lee and they both became friends and gradually fell in love. The ending quite actually does not satisfy me, or perhaps was unexpected.
Overall, this gets a solid 8.
Honestly speaking, if you have issues regarding blood phobia and gore then try not to watch it.