What would Karl Marx think?

The used-bookselling website AbeBooks’ biggest sale in 2011 was for a three-volume first edition of Karl Marx’s “Das Kapital,” with the first volume published by Otto Meissner in 1867. Ironically, someone paid $51,739 for the seminal critique of capitalism.

The second-highest sale on the site was for a first edition of Harper Lee’s “To Kill a Mockingbird,” published in 1960. This copy sold in May for $25,000; the high price tag probably came because it had been signed by Lee herself. Lee largely withdrew from public life after the publication of her first novel half a century ago. Signings are rare; she never published another book.

In spring 2011, Lee emerged from her quietude to issue a statement through her sister’s law firm repudiating an upcoming book, “The Mockingbird Next Door: Life With Harper Lee.” The book by Marja Mills, a former Chicago Tribune reporter, was said to be written “with direct access to Harper and Alice Lee (her sister) and their friends and family.” In the written statement, Lee said she had not cooperated with the author: “Contrary to recent news reports, I have not willingly participated in any book written or to be written by Marja Mills. Neither have I authorized such a book. Any claims otherwise are false.”

Meanwhile, Lee memorabilia has begun surfacing elsewhere. A number of letters and cards written by the author to a fan were sold in 2011 by Nate D. Sanders auctions. The chatty letters included thanks for gifts, the occasional note about her work and one letter that asked, “Please don’t put this on the internet.”

The Internet was one thing Marx wasn’t worried about.

A sampling of big-ticket sales from AbeBooks in 2011:

$20,447 — A first edition of J.R.R. Tolkien’s “The Hobbit,” with a correction on the back cover. The first printing, in 1937, was of just 1,500 copies.

$18,750 — 14 pages written by John Ruskin by hand in 1866 on a work by Thomas Carlyle, which Ruskin used for his essay “Notes on the Economies of the Kings of Prussia.”

$14,925 — Charles Baudelaire’s poetry collection “Les Fleurs du Mal,” published in 1837. Six poems were banned for their erotic content.

$10,500 — Pablo Picasso’s “40 Dessins de Picasso en Marge du Buffon” (40 Drawings by Picasso in the Margins of Buffon), a folio published in 1957, of which there were just 226 copies. Picasso signed it in green crayon.

$9,500 — “A Natural History of British Insects.” The 16-volume illustrated set was published from 1792 to 1813.

According to another used-bookselling website, Bookfinder, the most-sought-after out-of-print book in 2011 was Madonna’s “Sex.”