Earlier this month, the Duke of Portland copy of John James Audubon's seminal work Birds of America sold at Christie's for $7.9m.
This is a little way off the world record price for a book, which is held by another copy of the work, but it is still more than the price of any other single book ever sold at auction: the top three most valuable are all copies of Birds of America.
The book with its obsessively rich artworks depicting avians of the United States is always going to be valuable - but of course not all copies are equally so. The supremely valuable copies are those from the vast elephant folio edition.
Collectors with less extreme sums at their disposal can still own a different but still highly impressive copy of the work.
An example of this is going under the hammer courtesy of a Pennsylvania auction house this week. This is a tall copy in eight volumes in its original 3/4 brown morocco.
Presenting 500 hand coloured lithographic plates, the book is generally in clean, bright and fine condition, at least on the inside.
The outside is not in perfect condition, with spine ends rubbed at the corners, but it remains an impressive set which could serve as the centrepiece in a great book collector's library.
The set is listed at $10,000 - $15,000 in the auction which will conclude in the morning of February 2 (local time). Watch this space for the result.