Soo.. MAJOR SPOILERS BEHIND THE CUT.
So I thought I was INSANELY clever for figuring this out, but I am sure that many people have already solved it, or I could be horribly wrong..
So first let's go through the obvious theories. FIRST THEORY- Harry is the sixth horcrux? Therefore Voldemort is basically insuring his immortality, because afterall, he did kill Harry's parents which would have given him the opportunity to implant another part of his soul in any object of significance. That would also blatantly explain why he can't kill Harry, because then he'd be killing a part of himself.
AND second theory: R.A.B could be the initials of Sirius's brother, who supposedly died after deserting the Death Eaters. Yeah, I know, PERFECT FIT! It'd make sense that he'd be avenging his brother's death, or just opening a can of whOOPass on the D.E for trying to kill him.
And third theory: that Snape and Dumbledore have a giant plan together and Snape is not really a Death Eater at all because Rowling studied classic literature. I don't think she's stupid enough to set up Snape as the bad guy to have him ultimately end up as.. the bad guy.
NOW ONTO MY THOUGHTS ABOUT THE BOOK-
Reading through all the details made me realize just how much planning Rowling must've put into this book. Like the smallest things, when Harry is running through Hogwarts while chasing the Malfoy and Snape and is careful to jump over the vanishing step, those small details just show how attentive Rowling is for this series. I think this one was probably the most informative of all in the series. You basically find out everything else you need to know in this one book about Voldemort. All the pensieve sessions and mentions of Tom's EXTREME HOTNESS. I think I may love this Dark Lord now.
Love potion- sooo weird. Romilda- EVEN weirder. Ginny/Harry- At first I didn't like it AT ALL, mainly because I thought Rowling was going to write their relationship like she did Ron's and Lavender's, but she didn't. And in the end he has to be noble any ways and give her the old heave-ho. Ron/Hermione- SOOOO good. Ron/Lavender- SOOOO horny. Tonks/Lupin- SOOO Ashton/Demi, but still soooo good. And Bill/Fleur, a little WTF?! but whatever, I'll live.
And Harry/Ron/Hermione heading off on a HUGE adventure in the seventh book. HELLLSSS YEAH!!
Rowling going on a one year break to watch her baby grow up- SOOOO BAD. GIVE ME THE SEVENTH BOOK, DAMNIT.
And that's my shpeel on that.