Introduction ''In books lies the soul of the whole Past Time; the articulate audible voice of the Past, when the body and material substance of it has altogether vanished like a dream.'' Thomas Carlyle, ''The Hero as a Man of Letters'' (1841) What is a book? Technically, we might say it is any set of printed pages that are fastened together inside a cover. But what, then, of all those books that you can read on your electronic device? And how do we account for those ancient texts perhaps inscribed on a stone tablet or even the bones of a sacrificial animal? We have a rich literary history that far pre-dates the technology that gave us paper, let alone the wherewithal to bind that paper together and stick a cover on it. Better, then, to adopt a much broader definition - the book is a written work of fiction or non-fiction created with the intention that it should be read by others. On what material it was originally set down hardly matters. We are the only species, of course, to produce books: an object that encapsulates the ideas and imagination of its author or authors. The book has a unique status as an emblem of human culture and civilization. It is a vessel for sharing stories, dispersing knowledge, examining the nature of our extraordinary species and imagining what lies beyond our known world.

As Carlyle suggests, books ultimately provide an invaluable and comprehensive record of what it means to be human. Sometimes, they may even give us a window onto the divine. As Jorge Luis Borges once wrote: ''I have always imagined Paradise as a kind of library.'' This volume takes a curated list of fifty of the most influential books of all time, putting each into its historical context. From ancient game-changers like the Epic of Gilgamesh and the Iliad, through sacred texts and works of philosophical rumination by the likes of Confucius and Plato, via scientific treatises, historic ''firsts'' (such as the first printed book) and cultural works of enduring impact (think Shakespeare, Cervantes and Joseph Heller, these are volumes that are at once both products of their societies and vital texts in moulding those same civilizations. What this selection isn''t is a celebration of the literary canon, a reaffirmation of the ''best'' books from the past. You will find no Austen or Dickens here, nor Melville or Dostoyevsky or García Márquez. There is Shakespeare and Cervantes and Tolstoy, but not because they are somehow ''better'' than those others.

Rather, this collection aims to select books that reflect the passage of human history - mostly our progress and occasionally our regression too. Most not only reflect, though, but themselves changed how we think and live - not merely symbols of history but agents of it. By definition, they are ''important'' works and, in broad critical terms, ''great'' works too. But this book is not concerned with which works are the greatest of all - there are plenty of other volumes that try to figure that out, and good luck to them. Inevitably, making a selection such as this is highly subjective. It is a process as much defined by omission as by what is chosen. In selecting fifty titles, we can only hope to dip our toe (our little toe at that) into the vast pool of literature from ages gone by. In doing so, it is folly to make any claim for definitiveness.

Instead, we are playing a literary game. Which of the fifty choices are indisputable? Which are taking a place better deserved by some other work? Everyone will have their own ideas. In the end, it matters little that we all agree. More important is that by turning our minds to the question in the first place, we might meet some unfamiliar works, revisit some old favourites, and gain some insight and pleasure in the process. Books are brilliant. They are building blocks of our collective identity. They are monuments to our civilization. They are gateways to new worlds.

We cannot explore them enough. Carl Sagan summed it up elegantly: ''Across the millennia, an author is speaking clearly and silently inside your head, directly to you. Writing is perhaps the greatest of human inventions, binding together people who never knew each other, citizens of distant epochs. Books break the shackles of time. A book is proof that humans are capable of working magic.''.