What is name of worlds thickest book?

It's impossible to say definitively which book is the "thickest" in the world. Here's why:

* Thickness can be measured in different ways: Do we mean the most pages? The tallest stack? The heaviest book?

* There are many contenders: There are numerous incredibly large and heavy books, including encyclopedias, dictionaries, and art books.

Here are some contenders for the title of "thickest" book, depending on how you define thickness:

* The Guinness Book of World Records: Often considered the largest book by page count.

* The Oxford English Dictionary: This behemoth dictionary is famous for its extensive vocabulary and numerous volumes.

* The "Book of Kells": A beautifully illuminated manuscript with 680 pages, though it's more famous for its artistry than its sheer size.

* "The Encyclopedia of World History": A multi-volume encyclopedia spanning centuries of history.

Ultimately, the "thickest" book depends on your definition of thickness and what you're looking for in a book.