It may be the last book you'll ever buy. And certainly, from a practical standpoint, it will be the only book you'll ever need. No. It's not the Bible or some New Age tome promising enlightenment—al though it would let you carry around both texts simultaneously. It's an electronic book—a single volume that could contain a library of information or, if your tastes run toward what's current, every title on to day's best-seller list. And when you're clone with those, you could refill it with new titles. Why an electronic book? Computers can store a ton of data and their laptop companions make all that information portable. True enough. But laptops(便携式电脑) and similar portable information de vices require a lot of power and heavy batteries to keep their LCD screens operating. And LCDs are not easy to read in the bright light of the sun. Fact is, when it comes to portability, easy viewing, and low power requirements, it's hard to beat plain old paper. So let's make the ink electronic. That's the deceptively simple premise behind a project currently coming to fruition at the Massachusetts Institute of Technology. Some hurdles mostly having to do with large-scale manufacturing remain, so it will be a few years before you see an electronic book for sale in stores. But the basic technology already exists, developed at the Institute's Media Lab by a team led by physicist Joe Jacobson. Thanks to electronic ink, the book essentially typesets itself, receiving instructions for each page via electronics housed in the spine. From a power standpoint, this process makes the electronic book very efficient. Unlike an LCD screen, which uses power all the time, energy is no longer needed to view the electronic book's pages once they are typeset. Only a small battery would be required, as opposed to the large ones needed to power laptop computers and their LCDs. Convenience, though, is still the main attraction—and that means more than simple portability. Be cause the information is in electronic form, it can be easily manipulated. Jacobson thinks an electronic book will be affordable around $ 200 for a basic read-only model to about $ 400 for one that would record your margin scribbles. Some hurdles remain, though, before you can take an electronic book with you anywhere. Paper is produced in long sheets, and Jacobson is still working on the best method to integrate electronic ink into that process. To avoid having to use thousands of tiny wires on each page, the ink itself must be conductive. Such ink was recently demonstrated in the lab but has yet to be produced in volume. 'Essentially,' notes Jacobson, 'We're trying to print chips.' Jacobson is confident, however, that this can be done on a large scale. If Jacobson succeeds, he will have made the book for the 21st century. According to the passage, which book is the only book you'll ever need?