There is a beguiling rural quality about the town gardens as mothers picnic with their own and other people's children. It would come as no surprise to learn that the Spiegeltent's catering depended on a navy blue Aga. These days it can seem as if the Edinburgh Book Festival is the prerogative of the chattering and broadsheet-reading classes.
The Book Festival's director, Faith Liddell, is conscious of the railings round the tented site, and strives to combat the notion that these enclose some kind of exclusive enclave.
"Books are for everyone," she says. "There's an enormous potential for enjoyment and fun. Compared to the cost of many family outings, the prices of entrance and of tickets at the Book Festival are pitched relatively low."
But is this just an instance of preaching to the converted?
"No," says Liddell. "All kinds of people enjoy books, and all kinds of people come along. There's something for everyone.
"The Children's Programme is important. They come into an environment packed with books and see people enjoying them. It's more than just the events. They see and hear things and mix with grown-ups getting pleasure from books. It's a great experience, and of course we also promote reading."
Children attending the festival can discuss their favourite literature face to face with top novelists like Anne Fine, Vivian French, Jeremy Strong, Joan Lingard and JK Rowling, or poets like Michael Rosen, Roger McGough and Brian Patten. They can put their science questions to Russell Stannard (Uncle Albert) and attend workshops on how to write or make pop-up books for themselves.
In that case, is it not a pity that, no sooner does Edinburgh erupt into colour, excitement and creativity, than Lothian's schools open their doors?
For decades now, late August has been a time of bitter frustration for many Scottish teachers, tantalised by a brief taste of festive fun and culture. The good times roll, and they have to be back at their desks pdq. Just to rub salt into state schools' wounds, this year the independent George Watson's goes back on August 27, with St George's, Fettes and Edinburgh Academy even later. To them that hath, shall be given.
Lindsey Fraser, the co-ordinator of the Children's Programme, argues that the overlapping dates are an advantage: "Thanks to the organisation and dedication of class teachers, children who might never experience the Edinburgh Book Festival do so in school groups. Some staff even start the first day of the session by boarding a bus to bring a new class here. Then there's the knock-on effect if children bring their parents at weekends.
"We've kept the price at pound;1 per child for school group admission to events. Bookings this year include parties from schools in Killearn, Galashiels, Rosyth and Dundee. There's been a good response from secondary schools, and librarians as well as teachers are always supportive.
"We do outreach, for instance with Laurence Anholt to Wester Hailes Library, in conjunction with Edinburgh City Libraries. It's great, too, for authors to chat to their public, and benefit from feedback from the children. Via the schools, we can reach children whom otherwise their books might not reach."
So if Charlotte Square sometimes seems to be a seething mass of civil servants, teachers, managers, architects, media persons and the like, at least the matter of this imbalance is being addressed. On the other hand, unremarkable clothes, hair, voice and behaviour are not exclusively the badge of people in traditional middle-class occupations. To make any such assumption would be to judge a book by its cover.
Tickets for some events at the Book Festival (which runs from tomorrow until August 31) are still available, on 0131 624 5050.