This is a great book, I based my Vietnam cycling trip on the North by Northwest route described.
There were a couple of small drawbacks though, the book isn't entirely comprehensive and the maps could be better, however the altitude maps were crucial and the directions were certainly sufficient.
There are also some very useful recommendations. The only area I usually disagreed with was the restaurant recommendation section. The authours tended to select 'westernised' establishments, whereas I prefer to mix in with the locals to get the most authentic food, but I guess this is a matter of personal taste.
So overall a very useful book that made for a great holiday, with only a few minor points to be aware of.