Booking a profit: The authors who can make you money
The sign on the front of the bookshop says: "Kindles are banned from the Kingdom of Hay."
While it may be a joke, it is an indication of the passion felt by those visiting the Welsh town of Hay-on-Wye this week for its annual literary festival.
Even as digital downloads take an ever larger share of the market, books are putting up a surprising fight.
The UK market for second-hand books is worth around £500m a year, according to the Antiquarian Booksellers Association.
With the entry level for buying other investments, such as gold, art or property, spiralling out of reach, that is leading to renewed interest in physical books.
After all, you can trawl your local charity shops or car boot sales and pick up a bargain - if you are lucky.
End Quote Adam Douglas Peter Harrington Books
The most important thing in books is to get the first of anything”
"I have a friend who found a first edition of Philip Pullman's Northern Lights in a charity shop for a pound," says Tracey Martin, an author and antiques collector. "It's worth in excess of £2,000, depending on condition."Passion
So if you have a small budget, where should you start?
"The most important thing in books is to get the first of anything," says Adam Douglas, senior specialist in literature at Peter Harrington.
"That's what collectors are interested in. They want the first printing, the first publication, the first impression of any given book."
Potential investors should also look for the best possible copy they can find.
"You can always tell when you're looking at a collection if somebody has always gone for the slightly poorer copy because it was a little bit cheaper," says Tim Bryars, of the Antiquarian Booksellers Association.
"In the long term, buying the best will pay off."
Much like the advice on building art collections, book experts recommend investors avoid buying for the sake of buying.
"It's very difficult to start looking at it in a speculative way and say, 'I'm going to start collecting in that area because I think it's going to increase in value," says Mr Douglas.
"The only way you're going to get excitement and enjoyment out of it is to follow your passion."
Mr Bryars agrees.
"Buy what you love, buy what you are passionate about," he says.
"That's terribly important. Never buy a book purely as an investment. I can justify everything in my shop. I like it, I can see the point of it."Rediscovery
For those who do want to look at the market speculatively, there are many cautionary tales. Some authors become household names in their lifetimes and then move out of fashion.
A contemporary of Ian Fleming, the author of the James Bond books, was Alistair MacLean.
No less famous during the authors' lifetimes, MacLean's books were also iconic titles that became major films, from The Satan Bug to The Guns of Navarone and Where Eagles Dare.
Nonetheless, last December a first edition of Fleming's Casino Royale, with some nicks and tears, sold for £11,711 at auction.
A pristine first edition of MacLean's HMS Ulysses will set you back less than £500 - and that is by far his most valuable book.
Still, there are examples of out-of-favour authors becoming collectible once again.
Adam Douglas notes that PG Wodehouse has enjoyed a marked increase in popularity as readers rediscover his work.Big screen
Often it is other media that lead to a rise in an author's value.
A rare 1925 first edition of F Scott Fitzgerald's The Great Gatsby is set to go on sale in London for £120,000. Its price is driven, in part, by the new film.
"When big movies are out, such as Harry Potter, then suddenly you see this trend where people all want to purchase copies of Harry Potter," says Ms Martin.
"If there is a Roald Dahl film that comes out, then you really do see there is an increase in popularity."
So with your limited budget, do the experts have any tips on where to look next?
"If you haven't got a lot of money and you want to get into collecting books, I suggest looking at children's titles," says Ms Martin.
"There are a lot of books out there that are available for under £100, if you want to take a punt. And hopefully they will increase, in time, in value."