My 1992 edition has paid for itself time and again. Written very much from a practical perspective, this book deals solidly with topics which are either ignored or skated over by others.
When I was working on developing FX and MM trading systems, I found that the sections on MM and FX calculations were invaluable dealing as they did with the reality of FX and MM trading : calculating broken dates, forward forward rates, settlement dates and how to recalculate rates when there is a holiday in one or both currencies in an FX deal.
If you have anything to do with treasury front, mid or back office then buy this book.