It could be a record-breaking afternoon in the book world. Today, Christie’s New York will auction off a copy of John James Audubon’s Birds of America, which already holds the title of most valuable printed book in the world, having sold for about $11.5 million in 2010. In fact, according to The Economist , a true list of the ten most valuable single books ever sold would have to include five copies of The Birds of America. Though Christie’s is playing their cards close to the vest and estimating a $7 to $10 million sale, today could see a new record for the book. After all, the copy that sold for $11.5 million was estimated at less than the copy on auction today.

To help you brush up on your knowledge of the very old and very valuable, we’ve compiled a list of the ten most expensive books ever sold — no white gloves necessary. Click through for an overview, and then head upstairs to check your attics for any forgotten dusty tomes — you could be a millionaire and not even know it.

The First Book of Urizen, William Blake — $2.5 million

Originally printed in 1794, The First Book of Urizen is one of the major pieces (and some say the most important) in Blake’s series of prophetic works. One of only eight known surviving copies was sold at Sotheby’s New York in 1999 for $2.5 million to a private collector.

The Tales of Beedle the Bard, J.K. Rowling — $3.98 million

Before this book, meant to be the same children’s book that figures heavily in Harry Potter and the Deathly Hallows, became a mass-market paperback, J.K. Rowling created seven original copies, each one handwritten and illustrated by Rowling herself. Six were given to friends and editors, but in 2007, one of the seven was put up for auction. It was snapped up by Amazon.com for a whopping $3.98 million, making it the most expensive modern manuscript ever purchased at auction. The money from the sale of the book was donated to The Children’s Voice charity campaign.

Geographia Cosmographia, Claudius Ptolemy — $4 million

The world’s first printed atlas, and the world’s first book to make use of engraved illustrations, Ptolemy’s 1477 Cosmographia sold at Sotheby’s London in 2006 for £2,136,000, or almost $4 million at the time.

Traité des arbres fruitiers [Treatise on Fruit Trees] by Henri Louis Duhamel du Monceau, illustrated by Pierre Antoine Poiteau and Pierre Jean François Turpin — $4.5 million

Definitely the most expensive book ever written about fruit trees (featuring sixteen different varieties!), a copy of this lush, five volume set of illustrations and text sold for about $4.5 million in 2006.

The Gutenberg Bible — $4.9 million

A copy of the Gutenberg Bible sold in 1987 for a then-record $4.9 million at Christie’s New York. Only 48 of the books — the first to be printed with movable type — exist in the world.

First Folio, William Shakespeare — $6 million

Though the First Folio’s original price was a single pound (one or two more if you wanted it bound in leather or otherwise adorned), intact copies are now among the most highly prized finds among book collectors, with only an estimated 228 (out of an original 750) left in existence. In 2001, Microsoft co-founder Paul Allen purchased a copy for $6,166,000 at Christie’s New York.

The Canterbury Tales, Geoffrey Chaucer — $7.5 million

A first edition of the 15th century bawd-fest sold for £4.6m (or about $7.5 million at the time) at Christie’s in London in 1998. Of the dozen known copies of the 1477 first edition, this was the last to be held privately, and was originally purchased for £6 by the first Earl Fitzwilliam at the sale of John Radcliffe’s library at Christie’s in 1776. Talk about growing your investment.

Birds of America, James Audubon — $11.5 million

In 2000, Christie’s auctioned off a copy (one of only 119 known complete copies in the world) of Birds in America for $8,802,500. Ten years later, another complete first edition was sold at London at Sotheby’s for £7,321,250 (or about $11.5 million) Today, another copy of the enormous four volume set goes up for auction at Christie’s, and perhaps another world record will be made.

The Gospels of Henry the Lion, Order of Saint Benedict — $11.7 million

Originally commissioned by Henry the Lion, Duke of Saxony, for the altar of the Virgin Mary at the Brunswick Cathedral, this gospel book was purchased by the German government at Sotheby’s of London in 1983 for £8,140,000, or about $11.7 million (at the time). At 266 pages, including 50 full-page illustrations, the book is considered a masterpiece of the 12th century Romanesque illuminated manuscript.

The Codex Leicester, Leonardo da Vinci — $30.8 million

The most famous of da Vinci’s scientific journals, the 72-page notebook is filled with the great thinker’s handwritten musings and theories on everything from fossils to the movement of water to what makes the moon glow. The manuscript was first purchased in 1717 by Thomas Coke, who later became the Earl of Leicester, and then, in 1980, bought from the Leicester estate by art collector Armand Hammer (whose name the manuscript bore for the fourteen years he owned it). In 1994, Bill Gates nabbed the journal at auction for $30,800,000, making it the most expensive book ever purchased. But hey, at least Gates put his purchase to good use — he had the book scanned and turned into a screensaver distributed with Microsoft Plus! for Windows 95.