Phillip Garrido's bookcase was filled with Dean Koontz, Billy Graham and books about cats Photo: EPA  Google is currently at work on a massive project to create the world's largest online library. Its engineers have so far scanned 10 million titles and, despite the thorny, unsolved problem of copyright, have ambitions to collect many more. It represents a potential democratisation of literature way beyond that of the creation of the public library.  Apple, too, is rumoured to be launching a new "tablet computer" that will rival Amazon's Kindle and Sony's Reader in its ability to let you hold hundreds of works of literature in the palm of your hand. You can't stick your nose in the pages of the book and sniff it, and you can't write in its margins, but who cares? More people will be able to read more and more. That's good, isn't it?  Well, of course. But how will we know who those people are? I mean, really know them? It's not just middle-class twaddle to say that people are defined, identified, by the books they read. It's not only a question of which novels Barack Obama took on holiday (Lush Life, Plainsong) or who takes what to their Desert Island. Look, for example, at the case of Phillip Garrido.  Last weekend, a pesky photographer leapt over the wall of the squalid compound in which Garrido kept Jaycee Lee Dugard captive for 18 years. All of the pictures are interesting, of course – the tents, the mess, the fences, the poignant, abandoned artefacts of those sad, strange childhoods. But most fascinating of all is the shot of Phillip Garrido's bookcase.  For a start, it is crammed with well-thumbed, obviously well-loved copies of books. It is the bookcase of a bookworm. To grow up in a house without books is sociological shorthand for possible deprivation; a house with books is a privilege. The fact that Jaycee and her daughters were kept captive with an above-average-sized library is interesting in itself.  And then there is the content. As one detective said, on seeing the photo, "When we are dealing with paedophile suspects, it is often the books and less than obvious matter they have in their homes which provides the key to understanding." So it's significant that good old Billy Graham is there, on Angels, God's Secret Agents. Angels, eh? Then there is the ominously titled Dead Snails Leave No Traces, which sounds like it could be a textbook for a murderer, but is in fact just one of many works on horticulture. There's an Isaac Asimov, near a Patricia Cornwell, above a Danielle Steel. There are lots of books about cats. And there is a whole shelf just full of the science fiction/horror writer Dean Koontz.  Ah, poor Dean Koontz. Up to last week, he was probably feeling rather good about himself: the sixth-highest-earning author in America, 11 number-one bestsellers. He would have been justified, up until the weekend, in giving himself a pat on the back. And then it turns out he's the bogeyman's favourite author. That's the trouble with being a writer: you can't pick your readers, and you can't control how they take your work and use it to define aspects of themselves.  I've only read one Dean Koontz. The title eludes me, but I do remember a rather extraordinary denouement, in which a giant, marauding pumpkin terrorised the quiet suburban streets of America. Not my sort of thing, marauding pumpkins – or runaway fruit and veg generally – and the fact that they are not on my shelves says something about me: I don't like horror. The fact that they are on millions of other shelves says something about the owners of those: they do.  But horror was obviously too important to Garrido, and that detective is right. He and a lot of keen readers would have looked at that bookshelf and shivered. The toxic literary combo of horror plus thriller, cute fluffy kittens, dead snails and – the icing on the cake – angels does say a lot about Phillip Garrido. A lot more than a palm-top device would ever tell us.
The most fascinating picture of the squalid compound where Garrido kept Jaycee    Lee captive, is the shot of his bookcase, writes Gill Hornby.