I will say very little about this. It is much cheaper and orders of magnitude lighter than the printed version. It contains substantially the same material. On the other hand it is much harder to look material up. As I thought that a primary characteristic of design patterns was that they were not cut and paste recipes, I can think of little real reason for this product. Still it means that I can quote large chunks of Design Patterns from my laptop - it will impress all those that think I do so from memory. Most impressive is to have a paper copy with you as well and say something to the effect 'I think that you will find on page...' but perhaps you would like to check because my memory is deteriorating with the onset of old age.
Design Patterns CD
Elements of Reusable Object-Oriented Software
Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides
Addison-Wesley Professional (1998)
Book cover image courtesy of Open Library.