Ask HN: What's a good intro to quantum computing?

What's a good starting point for someone who has almost no understanding of quantum computing but a good understanding of classical computing?

When I read stuff about quantum computing, I kind of understand the words but really have no frame of reference to go off of :)

Some questions that always come to mind for me:

Is quantum computing going to be the 'next thing' that eventually replaces classical computing?

If a quantum computer can calculate all states of a problem at once, how do you know the right answer in amongst the infinite sea of wrong answers that you get?

How is a program actually written for a quantum computer?

Are there problems for which quantum computers are unsuited?

How do you actually 'run' a program, give it inputs and then get the outputs?

I'm really trying to get to at least some form of intuitive understanding of how a quantum computer would work. How would I, for example, boot one and ask it to find me the route from A to B on a map?