A first folio edition of Shakespeare's plays is to go on sale with an estimated price tag of up to £3.5 million.

Described by auction house Sotheby's as "the most important book in English literature", it was printed in 1623, seven years after Shakespeare's death.

The folio contains 36 plays, half of which had never been printed before and were it not for their appearance here they would have been lost forever.

Those 18 works include Macbeth, Twelfth Night, The Tempest, The Taming of the Shrew and As You Like It.

"William Shakespeare has had an impact on the artistic imagination, on language, literature and all the performing arts, more profound and more widespread than any other writer who has ever lived," said Peter Selley, Sotheby's English Literature Specialist.

"The first folio preserves 18 of his plays, including some of the most major, which otherwise would have been lost for all time.

"Relatively complete copies of the folio in contemporary or near contemporary bindings very rarely come to the market.

This sale will be a truly exceptional event."

The folio goes under the hammer at Sotheby's London sale room on July 13 and is expected to fetch £2.5 million to £3.5 million. Its original price was probably 20 shillings.

About 750 copies were printed and only about a third of these survive, mostly incomplete.

This copy is being sold by the trustees of Dr William's Library in London, a chiefly theological library established in the early 18th century under the will of Protestant dissenting minister Rev Dr Daniel Williams.

It retains its mid-17th century binding of plain brown calf skin and contains extensive markings and annotations that provide an insight into its early readership.

The copy has had the longest uninterrupted library ownership of any surviving example of the first folio, from at least 1716 until the present day.

Copies in their original binding very rarely come on to the market and there is only one recorded as remaining in private hands.

That copy belongs to the estate of the late Sir Paul Getty. ..SUPL: