From the Bible to Harry Potter, some of the world's most popular books have been challenged for reasons ranging from violence to occult overtones. In honor of National Book Lovers Day, here's a look at 10 classic books that have stirred up controversy.

1. THE CALL OF THE WILD

The Call of the Wild, Jack London's 1903 Klondike Gold Rush-set adventure, was banned in Yugoslavia and Italy for being "too radical" and was burned by the Nazis because of the author's well-known socialist leanings.

2. THE GRAPES OF WRATH

Though The Grapes of Wrath—John Steinbeck's 1939 novel about a family of tenant farmers who are forced to leave their Oklahoma home for California because of economic hardships—earned the author both the National Book Award and a Pulitzer Prize, it also drew ire across America because some believed it promoted Communist values. Kern County, California (where much of the book took place) was particular incensed by Steinbeck's portrayal of the area and its working conditions, which they considered slanderous.

3. THE LORAX

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Whereas some readers look at the title character Dr. Seuss's The Lorax and see a fuzzy little guy who "speaks for the trees," others saw the 1971 children's book as a dangerous piece of political commentary, with even the author reportedly referring to it as "propaganda."

4. ULYSSES

James Joyce's 1922 novel Ulysses may be one of the most important and influential works of the early 20th century, but it was also deemed obscene for both its language and sexual content—and not just in a few provincial places. In 1921, a group known as The New York Society for the Suppression of Vice successfully managed to keep the book out of the United States, and the United States Post Office regularly burned copies of it. But in 1933, the book's publisher, Random House, took the case—United States v. One Book Called Ulysses—to court, and ended up getting the ban overturned.

5. ALL QUIET ON THE WESTERN FRONT

In 1929, Erich Maria Remarque—a German World War I veteran—wrote the novel All Quiet on the Western Front, which gives an accounting of the extreme mental and physical stress the German soldiers faced during their time in the war. Perhaps unsurprisingly, the book's realism didn't sit well with Nazi leaders, who feared the book would deter their propaganda efforts.

6. ANIMAL FARM

The original publication of Animal Farm, George Orwell's 1945 allegorical novella, was delayed in the UK because of its anti-Stalin themes. It was confiscated in Germany by Allied troops, banned in Yugoslavia in 1946, banned in Kenya in 1991, and banned in the United Arab Emirates in 2002.

7. AS I LAY DYING

Though many people consider William Faulkner's 1930 novel As I Lay Dying a classic piece of American literature, the Graves County School District in Mayfield, Kentucky disagreed. In 1986, the school district banned the book because it questioned the existence of God.

8. LOLITA

Sure, it's well known that Vladimir Nabokov's Lolita is about a middle-aged literature professor who is obsessed with a 12-year-old girl who eventually becomes his stepdaughter. It's the kind of storyline that would raise eyebrows today, so imagine what the response was when the book was released in 1955. A number of countries—including France, England, Argentina, New Zealand, and South Africa—banned the book for being obscene. Canada did the same in 1958, though it later lifted the ban on what is now considered a classic piece of literature—unreliable narrator and all.

9. THE CATCHER IN THE RYE

Reading J.D. Salinger's The Catcher in the Rye has practically become a rite of passage for teenagers, but back when it was published in 1951, it wasn't always easy for a kid to get his or her hands on it. According to TIME, "Within two weeks of its 1951 release, J.D. Salinger’s novel rocketed to No. 1 on the New York Times best-seller list. Ever since, the book—which explores three days in the life of a troubled 16-year-old boy—has been a 'favorite of censors since its publication,' according to the American Library Association."

10. THE GIVER

The newest book on this list, Lois Lowry's 1993 novel The Giver—about a dystopia masquerading as a utopia—was banned in several U.S. states, including California and Kentucky, for addressing issues such as euthanasia.