From what I gathered in my online travels today, this book is heavily reliant on a software component, and that it requires some sort of irreversible registration to use said software. So it would seem that, unless the previous owner is willing to share the email address that the book was registered under, a second-hand copy would be near useless.
The reviews on Amazon (Not the most objective review, I know. But it gives one an idea) are also less than flattering:
http://www.amazon.com/Language-Proof-Logic-Jon-Barwise/dp/1889119083#messages.1889119083
The book is very expensive to buy from Armstrong's (R775 - I haven't yet enquired from Van Schaik's regarding price), but coming from Amazon it is around R500. I consider this a very high price for a book that stands to effectively become useless if the parent site, for some reason, were to become unavailable (no net connection, no computer access, site goes down, company goes out of business, etc). To give you some idea, most second hand copies of the book are selling for $10 or less (one used copy on Amazon is selling for $0.89!). That's a HUGE drop from R770/R500.
I'm personally not impressed by the lecturer's choice to use this book.
