the hexadecimal code is cut down to six essential digits for each letter.

the layout is not only a hint on how program is to be read, but also a part of the meaning.

there is one intentional spelling mistake in a certain word (not in the code), implicating  another component of the tenor.

also in the book:

words translated into musical notation,

the "Theory Of The Perfect Song X",

Anagram 1,

etc...