Yep, now you can read that can't-put-down book from your Kindle Reader, your iPhone and your PC.
I'm a big fan of Kindle. Being able to read the same book from nearly any location without ever losing your place or your bookmarks is quite an experience, though workplace productivity probably just took a big hit.
UPDATE: Tim Conneally has a review of Kindle for PC. Sounds like it's not yet ready for prime time.