Is human extinction likely?

I strongly agree that human extinction would be bad because it could prevent a lot of goodness, but is it likely to happen? I think the likelihood really matters; worrying about very very unlikely events seems similar to investing in the lottery.

I would like to be pointed towards articles and books about the specifics that inform whether we should think human extinction is likely. I really enjoyed reading What We Owe the Future, but it still seems very unlikely to me that something would happen that would kill enough people for us not to bounce back. Are there nuclear war scenarios I haven't thought of? Is there a way that a pandemic could reach everyone? I am especially curious of the estimations of people outside the Effective Altruism. 

Also, have EAs made cool bunkers yet? Can we spend a million dollars on bunkers and then do other stuff?

Thanks so much!