The first four Folios of William Shakespeare's "collected works" have sold for a combined figure of £2.479 million (US$3.64 million) at Christie's in London. The Folios – which were sold separately – were widely reported to have been snapped up by an anonymous American bidder, with the First Folio, which was published in 1623, fetching £1.874 million (US$2.75 million) alone. Widely regarded as a genius, Shakespeare – who along with his plays also wrote poetry – was born in Stratford-upon-Avon in 1564, and died in 1616. This year marks the 400th anniversary of his death. The First Folio refers to the first collection of Shakespeare's plays. A hugely important work, it contains 36 plays – half of which had never been printed before – including seminal works such as As You Like It . According to Oxford University it is "one of the most valuable books in the world." "The Shakespeare Folios… have a great aura to them," Margaret Ford, from Christie's, said prior to the auction. "The first Folio, for instance, has 36 plays. Plays like Macbeth and The Tempest, Antony and Cleopatra, only survive because of the First Folio, so it is an incredibly important work," she said. Ford added that the four Folios had become "the epitome of bibliophile activity."