Here's the hosting page for this challenge. She does a great job of setting everything out clearly and providing good links for reviews.
The challenge is to read books by European authors or books set in European countries. All genres are allowed, both fiction and nonfiction, including poetry, cookbooks, and travel guides. Each book must be by a different author and set in a different country. She provides the following list of countries. All are sovereign states that fall at least partly within the continent of Europe and/or have membership in international European organizations such as the Council of Europe. She does note that since, at present the UK is still one country, books for England, Scotland, Wales, and Northern Ireland all count as UK, at least for any prizes.
THE LIST: Albania, Andorra, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iceland, Ireland, Italy, Kazakhstan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Moldova, Monaco, Montenegro, Netherlands, Norway, Poland, Portugal, Republic of Macedonia, Romania, Russia, San Marino, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, and Vatican City.
There are five levels that you can participate at, from one book to five books, all with fun names. I will be doing the Five Star (Deluxe Entourage) level. I'm not really interested in the prizes, I just like doing the challenge.
The challenge runs from January 1, 2016 to January 31, 2017, but since I do it every year, I tend to stick to the calendar year rather than do overlaps. Overlapping with other challenges is encouraged however, and I often do that. Re-reads count, as do books in all formats.