Two centuries ago, in a poem titled The Biblomania, John Ferriar wrote of the "tall Book-shelf" that "Displays, yet guards the tempting charms within". Back at the start of the 19th century, books were expensive, precious objects, beyond the pocket of all but the rich or the truly devoted; the latter might have to choose between reading material and food.

At first glance today, when you wander into your local chain bookstore, its walls groaning as more "three for two" offers are stacked against them, it seems we're in a new age of plenty. And provided you're happy to stick with reading the latest airport potboiler or celebrity bio, you can stack your own bookshelves to your heart's delight, at a real cost that keeps going down every year.

But, if you want to read other things, you might be in more of a difficult position. I often review university press books selling for well over three figures in U.S. dollars – priced only to go in a few academic libraries, which are closed to the general reader.

Now I'm lucky, I have a 20-minute cycle-ride away from the spectacular private London Library, from which I can borrow at any one time up to 10 books that might all have that sort of value. And a 10-minute cycle away is the largest single physical repository of the world's knowledge, the British Library. So I can get access to pretty well any book I want.

But not everyone can live in the London NW1 postcode – it is quite crowded and expensive enough already, thank you, or even within range of the occasional visit. There have been developing, slowly, some digital alternatives.

I use Questia. Its coverage is patchy – there's a lot of out-of-copyright material from the Thirties and earlier, and quite a bit of recent stuff with which they've done deals with the publishers, but quite large gaps in-between. Still, at U.S. $100 a year – with lots of note-taking bells and whistles – it comes in handy. And, of course, there's the Amazon "search inside this book" facility, which can be useful in seeing if a book is worth chasing up.