Approximately 5 Billion bibles have been sold and that makes it far and away the biggest selling book in history - http://www.guinnessworldrecords.com/world-records/best-selling-book-of-non-fiction/

Be careful which blogs you read - the author of that blog used Wikipedia as his source and we should never trust Wikipedia. The blogger pulled his data from a fiction only book sales page so the only result one could expect to receive are fictional - https://en.wikipedia.org/wiki/List_of_best-selling_books#More_than_100_million_copies

Always check your sources and trust no-one - truth!