Among the hardest-to-find books are The Gutenberg Bible, "The Book of Urizen" by William Blake, "The Codex of Leicester" by Leonardo daVinci, and "The Birds of America" by John James Audobon. Few copies of these books exist, and as of 2015, each is valued in the millions of dollars.
In 1455, the Gutenberg Bible was the first book to be printed on a printing press. Seven copies are still known to exist, each valued at approximately $7 million as of 2015. "The Book of Urizen" is an adventure book written by William Blake. Filled with stunning relief etchings of angels and monsters, a copy sold at auction for $2.5 million in 1999.
Only one copy of "The Codex of Leicester" exists. It was daVinci's personal journal, and was sold for over $30 million to Bill Gates in 1994. Between 1827 and 1838, John James Audobon created a collection of every known bird in North America, and published them in a book titled "The Birds of America." The complete book sold in 2012 for $8 million. Individual pages fetch thousands of dollars.
First editions of well-known books are often valuable. The first edition of Miguel de Cervantes' "Don Quixote" sold for $1.5 million in 1989.