Hollywood made a movie about it!
Ergo, it must be true. Hollywood is well known for making films about true things, as opposed to entertainment-oriented fiction.
My favourites are the books and sites that tell you how to survive the impact of this planetoid. I'm pretty sure the energy created by such a collision would wholly liquefy the crust of the Earth, so surviving it would require a sustainable off-planet habitation. I am doubtful such exists and even more doubtful buying a book or a website entry would get me a place on one anyway.