Originally posted by Sam The Sham
Big book that you turn the pages on, no problem, big book program that turns the pages for you, big problem.
What's the difference exactly?
One of the differences is that books are based on actual played games by humans, and at some point you will inevitably 'leave' the book and have to think for yourself. If you use a chess engine, you never have to think and always can use the suggested engine move.
Another difference is that book moves might not be the best moves, since the book can be outdated, and the book is based on human analysis (computer assisted no doubt). So you have to be carefull even when playing book moves.