In My Book for a really enjoyable challenge. It came at the perfect time for me, as I'm trying to improve my German by reading. The challenge was to read as many books as we could in a language in which we are not fluent by the end of the summer.
I read Harry Potter und der Stein der Weisen and Anne Frank's Tagebuch. (Those reviews, auf Deutsch, are here and here.) I hadn't read Harry Potter before, but it was an easy read and good practice for me. And I acquired some fun vocabulary--dragon, goblin, monster, troll, etc. Anne Frank's diary was much more difficult, but I had read it in English years ago, so that helped.
Ekaterina encouraged us to write our reviews in the foreign language, too, which intimidated me, as I haven't written anything in German since college. But I did it, with a lot of sweat and effort, and much consulting of online dictionaries, lol. I also enjoyed very much connecting with a couple of other students of German and reading their work. And I got some helpful comments on the Harry Potter review from a native speaker, which was wonderful.
Looking forward to next summer's Language Freak challenge...