Seriously guys, read the Books of Sorrow. They give you so much background about what the Hive are and their motivations, that our entire struggle against them so far makes a lot of sense. It gives you context.
I wish I had read it before launch, or at the very least before The Dark Below. I don't think I've "spoiled" myself of anything because you'll never get these details in-game.
It's a short read, shouldn't take you more than an hour. It's not directly related to the game's timeline but gives you a backdrop through which to better understand what the hell is going on in this game's reality.
The first books are rather obtuse but once you're about halfway through it all starts clicking. It'll make your Destiny experience more enjoyable.
If you can't play today or for some hours, it's the perfect preparation.