Apple's iBooks and integrated iBookstore is now available for pre-download from the iTunes App Store [Free - iTunes link]. Due to licensing and the other insanities that keep publishing in the dark ages, it's US only for the time being, and while its purported 60,000 ePub-format catalog isn't the biggest, the integration with Project Gutenberg and ability to pull in other free ePub content will certainly keep you busy while Apple keeps ramping it up.
iBooks requires the just-released iTunes 9.1 to manage and sync iBooks ePub and DRM-free ePub content, so make sure you're all up to date. Then get reading and let us know how the experience compares to Amazon's Kindle, Sony's eReader, Barnes & Noble's Nook, and -- why not! -- one of them paper and ink real book jobbies!
Apple Guided Tour after the break!