The most widely read and studied book of the renaissance was the Baldassare Castiglione.
Latin was the most widely studied language 500 years ago. It was the language of academia, religion, and government across Europe and was used for scholarly and scientific writings.
English, followed by French.
The most popular and widely studied is the Norway lemming. Its latin name is "lemmus lemmus."
The Bible is by far the most widely purchased book.
The Diary of Anne Frank
The Lord of the Rings. By J.R.R. Tolkien, is the second most read book in the English Language. But considering populations I would expect the second most read book in the entire world would be one of three. The Bible. The Bhagavad Gita. Or the Koran. The Bible actually if you take the facts into account.
No European languages can be considered "common" in Iran, but the most widely studied foreign language (after Arabic) is English, which is a European language.
Quotations from the Works of Mao Tse-tung is the second most widely read book in the world. It is commonly known as the Little Red Book. There have been 820 million copies sold in the last 50 years.
No. Although English is the most widely studied language in Japan, less than 1% of the population claims fluency.
Uncle Tom's Cabin
No studies to support this, but probably the Bible, especially the Old Testament, which is studies by Jews and Christians on a regular basis (and by people of other religions when doing comparative religion studies.) There may be other works more widely studied in other languages. Chairman Mao's Little red Book would probably have been the answer twenty years ago.
The New England Primer