Thursday marks the 75th birthday of the artist Tom Phillips and much celebration is in order. He is best known for his ongoing project A Humument, new editions of which, in print and digital, coincide with this anniversary.

A Humument is an altered novel, begun in 1966 and first published in 1970. Phillips paints, draws and collages over the pages of an obscure 1892 novel – WH Mallock's A Human Document – leaving gaps for the original but transformed text to show through. Phillips has worked over the novel continuously through the decades: this year's edition will be the fifth. In 2010 A Humument appeared in digital form, as an app for iPhone and iPad. The technology suits it well: the brightly lit screen displays the pages at their best, as Phillips himself notes, "in colours more glowing than my pens and paints could achieve, almost like church windows at times".

What's really interesting about A Humument's digital counterpart is that it's not just a facsimile edition of the print version. Instead, Phillips implements something he's wanted to be possible all along: the ability to select two pages at random and gain an insight from the juxtaposition, in the tradition of such divination books as the I Ching.

"Very soon after starting the book in the 1960s I dreamed of its use as an oracle, and it has taken 40 years for technology to make that possible." He is so pleased with the outcome that: "I've become my own consumer. Each night after midnight I consult, somewhat furtively (even though alone), the Oracle I have made. I'm often surprised by pages made long ago and almost forgotten, as well as by the sometimes uncanny predictions they offer their maker."

As technologist Tom Armitage notes: "This isn't about the technology of display, the iPad. This is about the way delivery changes the relationship a reader has with a text, be it one they wrote or just one they've subscribed to." And we get the pleasure of watching it happen and experiencing it too. Happy birthday, Mr Phillips.