Lots of thought went into what dictionary was used. Portability was part of this - Have a stack of normal books you carry around, and you don't introduce the dictionary until later, and from your pocket. Another consideration was that the dictionary had to be easily available in large quantities. There was also a legal consideration that I won't get into details about - this dictionary happened to work while taking that consideration into mind. On a related note, there were similar legal considerations related to the books that work with Zodiac.
On top of all this, we wanted the dictionary to be recognisable. This is one of the most popular dictionaries currently sold. Yes, it is small, but as in all things we have to make certain trades. When it comes down to it, this dictionary ends up being a winner in our eyes.
// L
