That's an interesting promise. But there is a twist.
I take it you've visited http://www.adobe.com/products/digitaleditions/library/ Lots of ebooks there. But, yes, quite a number of them are only samplers.
And, likewise, you aren't going to find one site with all the free ebooks that will work with Digital Editions.
However, there are numerous sites with free ebooks (some of them samples, some of them just advertising stuff, some of them full books.)
And you can visit your local library and download - this time - full books from there.
So the promise was correct: millions of free books. But just not at the one site!
Does the Amazon Kindle work the same or would it be easier to use
I'm not an expert on these things, however, if you mean is there a central point for Kindle free books - yes and no.
No, for the reasons I indicated above. Also, my understanding is that the Kindle is Amazon's ereader product. Amazon would be more motivated to sell books than make free books avaiable
The yes part is: Amazon would have a vested interest to store free books somewhat centrally - with a view to encouraging you to purchase! Visit there!
So, neither is necessarily easier! (However, it would be interesting to know which has the wider range of books available. the Kindle platform or the ADE platform. I think it's probably much of a muchness.)