Charles Petzold

The ideal length of a song is 3 minutes. The ideal length of a movie is 2 hours. The ideal length of a book is 300 pages.

Of course, these "ideals" are really more like averages, and much leeway is allowed. There is nothing wrong at all with the lengths of "Der Abschied," Lawrence of Arabia, or Clarissa. But under the "life is too short" principle, we are usually inclined to favor movies and books of modest duration. We need more persuasion or confidence to begin tackling a work that's much longer than these ideals.

Whenever Deirdre and I are browsing the New Nonfiction section of a bookstore, we're always reading off intriguing titles or jacket copy to each other, but also checking the page count. A book that seems interesting at 300 pages needs to be a lot more compelling at 500 pages.

For that reason, I have sometimes tried to write 300-page books. I would very much like to write a 300-page book. But I have always failed.

All the time I was working on Code: The Hidden Language of Computer Hardware and Software (Microsoft Press, 1999) I always thought of it as a 300-page book. I well remember my horror when my publisher began laying out the pages and it was estimated to be coming in at about 400 pages. We tried a number of techniques to get the page count down: I cut a section on the symbolic logic of Lewis Carroll, pages were made a few lines longer than normal, and chapters were allowed to start on the verso (left-hand page) rather than being restricted to the recto.

The last page of text in Code is 382, and the last page of the index is 393, so at least we avoided actually displaying the dreaded 400 number.

Code actually has exactly 400 pages. As you might know, books are printed on large sheets of paper, which are then folded into signatures, pasted together, and trimmed. Most books these days are a size called octavo, which results from folding a sheet of paper three times into eight leaves or 16 pages. The total page count of a book — including all front and back matter — is thus a multiple of 16. Code contains 25 of these signatures.

I've always believed that Code would have been more popular had it been a 300-page book. (Not that the book lacks admirers — check out this recent video tribute — but Code has always seemed to have more of a cult fanbase rather than a mainstream audience.) I've even been tempted to try to made a 2^nd edition of Code by performing some ruthless editing. Every time I look at the book with that in mind, I'm at a loss figuring out what can go, so this will probably never happen.

It might be that 400 pages is a "natural" book length for me. Some of my recent programming books have been about that length:. Programming in the Key of C# (Microsoft Press, 2003) has 27 sixteen-page signatures, Programming Microsoft Windows Forms (Microsoft Press, 2005) has 25 signatures (the same as Code), and 3D Programming for Windows (Microsoft Press, 2007) has 28 signatures.

The Annotated Turing: A Guided Tour through Alan Turing's Historic Paper on Computability and the Turing Machine was, like Code, always intended to be a 300 pages in length. Surely 300 pages is sufficient to discuss a single 36-page mathematics paper! The first eleven chapters that I completed in 2005 covered the first 60% of Turing's paper and came in at 204 pages. I confidently asserted that the book was 2/3 completed.

Once again, I underestimated. When Wiley began composing pages, the estimated page count was coming in closer to 400 than 300, and once again, I was horrified. I tried cutting some stuff — a page or so in Chapter 8 that I could barely read without falling asleep, some unnecessary detail in Chapter 17 — but there wasn't much I could do. I wouldn't have minded deleting Chapter 13 in its entirety, but that would have required also deleting Section 10 of Turing's paper! This might well be the most expendable section of Turing's paper, but it simply had to stay.

I suggested tightening some of the spacing that separates Turing's paper from my commentary, but I think that would have been a disaster. This book contains a lot of different looking stuff in it, including regular math, strange tables, odd fonts, peculiar strings of characters, and the "air" in the layout is necessary to maintain at least the aura of readability. All of the chapters begin on rectos, which in the book business is certainly a touch of elegance. Most importantly, the book doesn't seem cramped.

In the end, the page count wasn't too bad. The last page of text in the last chapter is numbered 359, and the entire book contains just 24 sixteen-page signatures.

I am extremely proud to report that The Annotated Turing is my shortest book.

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