Since all the Harry Potter fans are here, can I ask a substantive question? And I guess I should put a Spoiler Alert here just in case.
I was really expecting some explanation of how Snape was able to deceive Voldemort (maybe he had an Unbreakable Oath with someone that somehow prevented Voldemort from detecting lies). Was there an explanation I just missed?
Got the book late, so by the time I thought to ask this question the spoiler thread was done.
Snape was an expert in Occulamancy (sp). That is why Dumbledore sent Harry to him to learn about it. I think the implication is that Snape was really good at it, better than Voldemort could detect. That and his love for Lilly was the power for it. Which it was state, was something Voldemort could not overcome or understand.
Remember in the "Order of the Phoenix" Snape was trying to teach Harry "occlumency" so that Harry could block his mind from the Dark Lord. Even Dumbledore recognized Snape as the expert on this.
There's also some indication that was why LV didn't know Narcissa was lying to him (there toward the end).
'twas beauty that slayed the beast...