By the book

LONDON: A rare copy of John James Audubon's Birds of America, billed as the world's most expensive book, is for sale alongside a first edition of Shakespeare's plays.

One of only 100 or so remaining copies, Birds of America is valued at between £4 million and £6 million ($6.73 million and $10.1 million).

A Shakespeare First Folio from 1623 is expected to fetch at least £1 million ($1.68 million).

The books will be auctioned at Sotheby's.