One other thing, to get to the Market, it should be an app already installed on your phone, normally looks like a white/green shopping bag. If its not on the homescreen, you'll probably have it in the app drawer, which is the icon that looks like a bunch of squares.
I'll nth the comments from everyone else, the Kindle app allows you to view books designed for the Kindle device, without needing one (just an Amazon.com account). There are free books, there are regular books. And just like with a regular Kindle, if you buy a book before it is available, it will be available on release day.
Along this line, if you want to go maybe the Barnes and Noble route, you can get the Nook app for the phone. Borders' Kobo device also has a corresponding app on our phones as well. Neither need the actual hardware device to work.