The short version: Hachette (a publisher) and Amazon (an evil behemoth) are in contract negotiations. Amazon wants more money from Hachette; Hachette doesn't want to give Amazon more money. Which is fair enough - businesses are there to make money so it's reasonable for both of them to want a bigger slice of the pie.
What isn't reasonable is what Amazon did next.
They started giving three week dispatch times on books by Hachette authors. That's not "we'll ship it and it'll take three weeks to get to you", that's "we'll ship it in three weeks even though it's in stock". Yes this is hitting Amazon's profits, since customers might take their custom elsewhere, but given the size and global position of Amazon this is hardly going to affect their bottom line. It's going to hit the smaller Hachette much harder.
And it's going to hit their authors.
The next thing Amazon did was remove the preorder buttons from Hachette titles - as can be seen in a screenshot in this blog post by the New York Times. This might not seem like a big deal, but it has a massive impact on authors since preorders are one of the ways in which publishers decide whether to buy more books by their authors. It's entirely possible that mid-list authors are going to lose their careers over this.
Last night I saw the following Tweet from Hachette author Nalo Hopkinson.
That's not what's happening. Instead indie bookstores (who are also hurt by Amazon's increasing market share) are promoting that they can get readers Hachette books faster than Amazon can, and they're doing it at a discount. Authors and readers are sharing the links, and the articles condemning Amazon's practices, and asking people to shop elsewhere.
I certainly will be. Pretty much everything on my wishlist are things I can buy elsewhere. Except for the Kindle books, and I'm really regretting the Kindle as my choice of e-reader right now. I can go to Smashwords for some of the indie and self-published books, but for titles from larger publishers I'm stuck with "buy the paperback" (which I bought an e-reader to avoid doing) or "don't buy it at all" (which also hurts authors).
It also puts me in a sticky position as a self-published author. My books are currently available on Amazon. If I take them down I could be hurting myself in lost sales, and I'm denying readers the choice of where to buy in the same way that Amazon is. If I don't, I'm supporting an exploitative company that, when it's finished taking on the traditional publishers, will probably turn on indie authors too.
For the moment the books and links are still available. This may change. I'd personally rather anyone planning on buying the Kindle edition of one of my books does so through Smashwords. You can download in multiple formats, which is handy if you want to change e-reader too.
Amazon has deep pockets. It's going to take a lot to make them notice that people are upset with them. Customer experience is apparently their core ethos: what will be telling is if they continue to behave like they don't care.