Women please note that high altitude can play merry hell with your menstrual cycle. It is important to point out that the guide differentiates what it knows from what it has been told. Also, new editions come out every year, although I would doubt that all the data could be checked annually, making the book far more up to date than its competitors. Apart from its style, which may tend to irritate rather than amuse, another problem is the guide's unwillingness to elaborate on what the author has researched personally, as opposed to what he has been told. Also, as only one country is covered, anyone thinking of crossing the border briefly to Peru, say, would have to take either two books, or borrow someone else's while over there.
New editions come out every few years.
Effects include a certain resistance to the effects of altitude, greater endurance, and a numb mouth. For those with a little more time, it might be preferable to fly into Caracas or Bogota, and continue overland. The major indigenous languages are Aymara and Quechua, but I met only a handful who could speak just these. There is no black market. In addition, cash withdrawals on a credit card are reportedly possible in some cities.