For Dutch readers and those familiar with Dutch the books are well worth the money, but that is of course for the individual to decide- not everybody can afford to spend 160 euros in one go for four books, quite apart from exchange rate and shipping for those not living in the Netherlands.
Unfortunately for non-Dutch speakers, the books are in Dutch apart from telegrams and correspondence with the Admiralty, operational orders, patrol reports etc which were originally written in English- these are included in the original language. I'm not sure whether these books would offer very much to them apart from curiosity value plus of course the many photos.
The publisher has this about the books on his site (in Dutch):
Babelfish or some similar programme can probably manage a translation.