Memory or rote learning has also got a bad name in society with our education system focusing on the processing of information rather than on remembering it. While Joshua and a few others do say that knowing how to remember is important in society, I as a scientist, tend to lean on the side of understanding rather than remembering (especially as Google remembers everything). Joshua Foer foresees a not too distant future in which technology directly communicates with our brains and information is directly accessible to our brains - making memory all but a forgotten skill.
The technique also involves visualizing numbers (or playing cards) one wants to remember. A person develops a system whether a two digit number (or cards) is typically replaced by an image in the memory palace. So, a person has a particular image for each number from 00 to 99 (or all 52 cards). While this is tedious at the beginning, Joshua takes us on an amazing journey in this book during which practice converts him (average in terms of memory at the beginning of the book) to one with extraordinary recollection. Joshua is himself able to remember a whole deck of cards in about a 100 seconds by the end of the book during the memory competition.
The Competitive Spirit:
Joshua also provides a glimpse to the mindset of a person who is competing in a national event. He talks about practicing and hitting the okay plateau beyond which he found it difficult to improve. The okay plateau is what we invariable hit after repeating a particular sport or action many times and we cannot improve beyond this point just by normal practice. Experts use deliberate practice in which they practice on the bits they keep failing at (or are not an expert on) to improve beyond the okay plateau. He also talks about his efforts to improve his concentration, diligence to practice every single day, and his attention to compare his performance with his competitors add to the aura of the book.
What I found fascinating about the book was Joshua Foer's attempt at what he calls participative journalism. In the sciences, this would be equivalent to a journalist performing the experiments to have a deep understanding of its caveats in the findings before writing an article about it (and wouldn't that kind of science journalism be refreshing in this day and age? - this could solve a number of problems in science). No doubt he has shown that the art of mnemonics is accessible to the average human being provided (s)he is ready to practice and put effort into becoming an expert at it.