A first edition of J.K. Rowling's Harry Potter and the Philosopher's Stone with the author's scribbles about the Hogwart's coat of arms and other details of the wizarding universe sold for £150,000 ($234,000 Cdn) at a charity auction in London today.

Also on offer was an edition of Life of Pi, in which author Yann Martel explains why the chapters are switched from the original Canadian edition, which sold for £2,500 ($3,900) and a first edition of Margaret Atwood's The Blind Assassin that went for £3,500 ($5,460).

The campaign First Editions, Second Thoughts was being spearheaded by the British arm of the writers' rights association PEN, which champions the freedom to read and write.

English PEN asked 50 acclaimed authors to "scribble second thoughts, marginalia or drawings" on first-edition copies of one of their famed books. The resulting titles were sold by Sotheby's London as a fundraiser.

"This is the first time that we know of that such a sale has been put together. Authors generally will write notes or whatever. They may annotate their own works as a copy for friends. They may have put an occasional note. We know no instance where an author’s been asked to go through and annotate and add additional information to the text," Sotheby's book specialist Philip Errington told CBC News.

"The responses are as varied as the books are varied," he added. "Tom Stoppard, for example, crosses out an entire page and puts 'Overkill' on the side. You’ve got other sources of inspiration. For example, many authors will give you a little note at the bottom to say 'This came about because...’ But then, other authors have annotated in other ways such as illustrations, etc."

Many of the writers offer interesting commentary, including Scottish writer Rowling, who scrawled about 1,000 words and 22 drawings into a copy of Harry Potter and the Philosopher's Stone. She notes that she devised the wizarding sport of Quidditch "in Manchester after a row" with a former boyfriend and even shares a what-if moment about one of the houses at her wizard school Hogwart's.

"Perhaps Hufflepuff house would have the respect it deserves from fans if I'd stayed with my original idea of a bear to represent it?" Rowling scribbled.

Meanwhile, Canadian writer Martel turned a copy of Life of Pi into an illustrated flip-book depicting a little boat moving across the sea. His notes include a couple of sentences about how he "never liked the first line" of his author's note and marks the spot where the novel's chapters differ from the original Canadian edition.

For his part, Kazuo Ishiguro shares a relaxing, beachside anecdote about how a group of writer friends helped devise the title to his award-winning post-war novel The Remains of the Day, about an British butler who revisits key past relationships.

Other top writers, illustrators and poets who have contributed books to the auction include:

  • Quentin Blake (Matilda)
  • Nick Hornby (Fever Pitch)
  • Hilary Mantel (Wolf Hall)
  • Ian McEwan (Amsterdam)
  • Philip Pullman (Northern Lights)
  • Andrea Levy (Small Island)
  • Tom Stoppard (Rosencrantz and Guildenstern are Dead)
  • Alexander McCall Smith (The No. 1 Ladies' Detective Agency)
  • Andrew Motion (Goodnestone)
  • Michael Morpurgo (War Horse)
  • Helen Fielding (Bridget Jones' Diary)
  • P.D. James (Death of an Expert Witness)

The final, 51st lot being offered is a fountain pen from Stephen Fry that has been engraved with a quotation by the British actor, writer and broadcaster. Graham Short, known for creating miniature engravings that can only be seen through a microscope, has marked the pen with the phrase: "Waggled in the right way, this inkly little stick can change the world."