Cry the Beloved Country is a great one about South Africa and is on the tenth-grade reading list at our school. It's not particularly difficult. My students normally enjoy it. The Power of One by Bryce Courtenay is another excellent world lit. book; it, too, is set in South Africa but gives an interesting look into the tension between the Germans, British, and Black South Africans during WWII. It's considered a young adult novel.
I agree with Post 4 that What Is the What is an pertinent book for current problems in Darfur, but I've had a lot of problems with that book. All of my students who have chosen that for independent reading (these are honors students) have had a very difficult time following the flashbacks and the author's style. They liked the basic storyline but were so frustrated that they would not recommend the book to others.
If you are looking for a good nonfiction book, Diane Ackerman's The Zookeeper's Wife is a great read. It should be on your students' reading level, and it tells the true story of a zookeeper and his wife who hide Jews in parts of the Warsaw Zoo during World War II.
A good Swedish modern writer is Stieg Larsson who writes The Girl Who . . ." series. They are interesting contemporary mysteries, but you have to consider your students and their parents because some of the books deal with some pretty dark parts of the human existence. If your students' parents don't have a problem with Khaled Hosseini's works, then they most likely won't have a problem with Larsson's.