Kathy, Ruth, and Tommy grew up together at Hailsham where things were never what they seemed. Guardians watched over them, art was gathered for the 'Gallery,' and they grew up with the knowledge that someday, when they left Hailsham, they'd become carers and eventually, donors. 
 At first, this was a bit difficult to get into as although terms such as 'donor' and 'carer' were used, they weren't explained until later in the book. However, once you get past that, it's an excellent read. 
 Kathy is the main character and in short, she tells her life's story. From meeting Ruth, talking to Tommy, and eventually leaving the Cottages to begin work as a carer. More importantly, she and Tommy end up learning the truth behind Hailsham and why precisely it is that they become donors.