Books like the Bible are the most printed, but it's difficult to get reliable figures on religious books because a lot are given out for free. A Tale of Two Cities by Charles Dickens has sold over...
The Bible is the best selling book ever.
The Bible is by far the most widely purchased book.
The best selling comic book would probably be a comic book from the Marvel series.
A list of the best selling horror books, as well as books of other genres, can be found at http://www.bookbests.com