Question about the title "Harry Potter and the Half Blood Prince".

I think it's because in this book there are some serious doubts about Snapes loyalty and at the end of it the characters are left with the conviction Snape is a traitor,a spy,a turncoat.

I hope it helped.

It was just a couple of minutes ago that I filled out a Sorting Quiz for one of the Picks. The result was 13 points for Gryffindor and 13 points for Slytherin. I thought it was bullshit, but now I see its point. To get to the bottom line, I can think of two possible options or - both my Slytherin and Gryffindor part can think of one.
The malicious explanation is that Rowling made up the whole Snape story during book six - to spice things up, maybe. This is really an evil theory of me, but I find the Snape thing so artificial and far-fetched that I can't think of anything else.
The Gryffindor point of view is of course that after Voldemort's return was revealed, the situation of the wizarding community is getting graver and graver. They are heading right back into the bad old days when nothing and nobody seemed what it actually was. With Dumbledore death the last barrier defending peace and security passed away at the hands of someone people thought to be worth of their trust. In the previous books we could see this tendency from the beginning. There was always somebody out there who wasn't who he - or she - was thought to be. Squirrel, Gilderoy Lockhart, Sirius Black and Peter Pettigrew, Moody, the Ministry of Magic, Snape. Feel that the significance of these people are increasing? A teacher, a celebrity, criminals, criminal hunter, the very government being in charge and the person closest and most trusted by Dumbledore, the only one who Voldemort ever feared. And no, this couldn't be McGonagall, because she had no access to Malfoy or Dark Magic and was always above suspicion. On the other hand there was always some amount of tension around Snape (Harry's broom, hating Sirius, spying and his actual past). He had always been the first one the Golden Trio pointed at in search of the responsible, so - as almost everything in Harry Potter - this had to come down to something. What exactly? A book titled Harry Potter and the Half Blood Prince ending with Dumbledore's death, leading into the second wizarding war.

Its because (I think) Harry used the Prince's book so much, and thought that he really knew the Prince, thought that he was a good guy. At one point, he even wondered if it had been his father, only to find it was Snape's book - the teacher who he hated and hated him back equally. The same teacher whom he wondered about his true alliance. The same teacher who killed Dumbledore - Harry's mentor.

The book is named after Snape because he's a frigging legend!! XD

He is known as the Half Blood Prince because he is a half blood and his mothers name is Eileen Prince (Prince being her maiden name)but idk why it is based around Snape...well from Snape being in it so much we get to see more of Draco and how Draco is now a Death Eater...plus with Dumbledores death and all...sorry this is probably a really stupid answer...

Idk the awnser 2.