We've been asked this question many times.

• Books in the previous centuries were made differently. They were made using paper that wasn't as cheap as the paper used today, and was mostly acid-free. Certain publishers these days have gone back to using acid-free paper, but most books these days use heavily acidic paper from a manufacturing process that makes it degrade very quickly, and is especially vulnerable in hot, humid climates.

• A lot of the books in the olden days were hand-sewn, not glued together in factories, and therefore are able to endure for several generations. You will seldom find a well-bound well-taken-care-of leather book falling apart even a century later, while most mass-market paperbacks sometimes disintegrate and yellow within a decade.

• The books bound in leather from some of the earlier centuries and even those made by fine presses today look and feel spectacular - this is because cattle were fed properly, and their skins were thicker; they did not end up in huge cattle farms and abattoirs as we have today. The difference between a leather-bound book and a cloth-bound book is not unlike the difference between a leather shoe and a canvas shoe. They feel, look, smell, and weigh different.

• The designer would often be a skilled craftsman who had honed his trade for some time before becoming a professional binder/designer himself. The ornate designs on covers are often individual designs blind-stamped or gilded into spectacular patterns.

• Many collectible books are gilt in gold along all the edges - these not only look beautiful but also protect the text block from moisture, dust and other impurities.

• Books with marbled endpapers have a special quality - marbling is a painstaking process that helps develop coloured patterns on paper using natural pigments; each design is unique, and stays with that particular book, never to be reproduced again. It is a function of chance and chemistry, and a perfect frozen image of the interaction between the elements that the marbling artist and his/her environment happened to produce. The endpapers also help protect the text block from damage.

• Pure investment potential: books that cost $10 to begin with can cost several thousand a decade or two later. But this requires patience and prescience, and is probably a slower way to make money than the stock market. The potential, nevertheless, is tremendous.

• Lastly, there is also a sentimental/historical value. Books that are over a hundred years old have survived many journeys, been through more than our previous three generations combined, and have "experienced" things in lands and times and cultures very distant from ours. A book that old carries with it all of that experience - of riding in carriages, of sitting on a heretic's shelf in the days of witch-burning trials, of lying next to an important personality at his/her deathbed, or of being a part of a family's heirloom for generations. It's like Frodo's Ring! Passing from hand-to-hand, generation-to-generation, it's a constant that runs through random, disparate lives. Maybe there's some value in that.

These days, poorly made, mass-produced hardcovers often sell for the same price as an old, beautifully-bound book. In case of the former, you're paying for the rents of the publishers and retailers, the CEO's fat bonuses, and all sorts of random costs that have been transferred over to you which are quite irrelevant to the value of the actual book - which usually costs less than three dollars to manufacture. In case of the latter, you're paying for the actual craftsmanship, design and care that went into producing the book, and the adventures that are carried with it.