I'm delighted with your question of what is different in the most recent chapman's Piloting and Small Boat Handling and may well buy the latest when it is published. Perhaps it will be available for the e-readers and iPads. However i do wish to let you know that there has been a great deal of difference from the early edition of 1917 when it first came out. You would not recognize it from the present edition as it was only 7 by 5 inches in size and less then a half inch thick.
In the 1917 edition there is barely a mention of sailboats other than to keep out of their way. Compass and charts were important and lights had a requirement of lens of fresnel or fluted of 16 square inches. While there is a complete chapter on the compass and its deviations, another chapter deals with nautical instruments....such as the Chip Log (with an Hour Glass) to measure boat speed, the Patent Log for those more wealthy, the Chronometer and the Lead Line. The recommendation was to forty fathoms which meant dropping a line 240 feet. Oh how I like my depth sounder.
But one thing has not changed much in all these years...that of Flags and Colors. I find it interesting that there were owners' flags, owners' dinner flags, guests flags and crew meal pennant. One flag has escaped my understanding and perhaps some of you can help....that flag being "the night pennant". For what reason would you fly that flag? I wonder.....
I suspect the newest edition will have something to say about iPads and apps and probably a fair amount about piloting using the latest GPS screens and hopefully it will also talk about AIS, automated Identification system. There has been many changes since 1917 when Motor Boating published the first little book in our sport.
Thanks for the question--I'll be looking forward to the latest publication...hopefully on my iPad (it won't weight as much as the hard bound edition.).