This is a huge development. While Amazon is clearly dominant in the US, it has only a few stores in Europe (UK, France, Germany, Italy, and just recently Spain), and its collection of local language books is, uh, irregular. The Kindle, to my knowledge is sold only through Amazon UK and US, though people in other countries can order it from Amazon US. (Michalis tells us in the comments that Kindle is also available in Germany for sales to that country, Austria, and Luxembourg.)
That means that Apple has a tiny window of opportunity to establish a foothold in Europe by making it easy for publishers to sell books in the local languages of each country. I hardly think it's a coincidence that Apple opened iBookstores in 26 additional European countries mere hours after Amazon announced its new Kindle Fire.
And note that publishers who are already in iBookstore (say in the US or UK) have already signed contracts for distribution in most of Europe. Only Denmark, Sweden, Norway, and Switzerland require new paperwork. And, Apple doesn't have to bother with paper books like Amazon does.
So Apple has the infrastructure up and running, all they need now is to encourage publishers to make their books available.
Just because the territories are listed as options for selling your ebooks does not mean that the iBookstore itself is live. I have heard from readers in some countries that say the iBookstore there is indeed live, and from others that there is some system maintenance going on.
This seems to be an everchanging story, so I'll use this blog post to add updates.
iBookstores confirmed live: Netherlands, Greece, Spain, Ireland, Lithuania, Finland (29Sep11) (and US, UK, France, Germany, Australia, and Canada) If your local iBookstore is live, please send me a screenshot!
Adding your ebooks to all of these stores is straightforward and easy, although the UX is pretty abysmal. Just go to iTunes Connect, go to Manage Your Books, choose your book, click Edit Rights and Pricing, click Add New Territory, choose the desired country, set the price and other options (I just choose Jan 1, 2011 because it's quicker, and it uses today's date), click Save and then go back again to choose the next new territory.
How to create a link to an ebook on a particular iBookstore? The easy way is to use the iTunes Link Maker. Search for your book in the country of your choice, and it'll generate the proper code for you.
Or you can create one by hand. The URL will look like:
Change the country code to the country of the iBookstore you're interested in. Wikipedia has a handy table.
According to Mark Coker of Smashwords, if you click on a link and get to a page in the local language of that store, that means the book exists (and ostensibly the store is live). If you get sent to iTunes, that means the book is not available in that country's iBookstore.
I'll update this post as more information surfaces. If your local iBookstore goes live, please let me know (and/or send me a screenshot if you can).