Harry learns about Voldemort's family and his foe's evolution into a murderer obsessed not only with power but with gaining eternal life.Dumbledore shows Harry a memory involving Slughorn conversing with the young Tom Riddle at Hogwarts, which has clearly been tampered with.Harry's attempts to repair things between the two fail, resulting in Ron going out with Lavender Brown and making Hermione jealous.
Harry develops feelings for Ginny, but is reluctant to pursue her for most of the year because of his friendship with Ron.
Following a wild Quidditch victory Harry and Ginny finally strike up a relationship, with Ron's reluctant consent.
Bellatrix feels Snape will be of no help until he surprises her by making an Unbreakable Vow with Narcissa, swearing on his life that he will protect and assist Draco in his mission.
Dumbledore picks Harry up from his aunt and uncle's house, intending to escort him to the Burrow, home of Harry's best friend Ron.
After a class contest, The Half-Blood Prince's tips help Harry win a bottle of Felix Felicis, more commonly known as "Liquid Luck." Though Harry's success pleases Slughorn, his newfound brilliance in potions angers Hermione, who feels he is not truly earning his grades and does not trust the Half-Blood Prince.
Believing that Harry needs to learn Voldemort's past to gain advantage in a foretold battle, Dumbledore schedules regular meetings with Harry in his office.Amidst these lessons, Ron starts dating a girl named Lavender Brown, and so Ron and Hermione start yet another quarrel.Also during this time, Dumbledore and Harry use Dumbledore's Pensieve to look at memories of those who have had direct contact with Voldemort.Ron and Lavender break up when Lavender sees the two of them walking out of the boys dormitories together.However, this was only because she hadn't noticed Harry walking ahead of them.There were many controversies before and after it was published, including the right to read the copies delivered prior to the release date in Canada.