Originally posted by: xMarauderx
Easy...
The book is fifty years old because it belonged to his mother...Eileen Snape nee Prince.
His mother was a "Prince"...and she married a muggle Tobias Snape..and so Snape is a half blood. And from his mother's side of the family..he is a "Prince"..so he made up the title.."Half Blood Prince"
I think this question has been asked many times before.
Yup!
That makes sence, n in the end heromine came back to Harry n told him that she was right n stuff.
-Aastha