It's aimed at teenagers, I would say.
But - like many other teenage books - it would be appreciated by adults too.
There are some 'issues' - sex, drugs, etc., but handled sensitively. I wouldn't recommend it to 11 yr-olds, but I wouldn't object to my 10 yr-old reading it.
I find this whole "suitable for age.." business very tricky. I was reading adult books by age 12 or so, and some of them were very unsuitable. I would prefer teens and tweens to be reading 'teenage' books even if they are pushing the boundaries a bit.
Many 8 yr-old girls are reading JW books with some harrowing details and content, as well as watching hours of soap operas, which I don't agree with. But 11-13s are hardly going to be corrupted by a bit of sex/drugs handled sensitively in a book. At least I think not.
This book does have some fairly explicit, though brief, sex scenes, and swearing.
from the blurb:
Everyone has to die. We all know it.
With only a few months of life left, sixteen-year-old Tessa knows it better than most.
She's made a list though - ten things she wants to do before she dis. Number one is sex.
Starting tonight.