This lavishly illustrated book is an indispensable guide for collectors of Royal Crown Derby paperweights. However, because RCD issue so many new paperweights and different colourways of existing ones, any book would become out of date as soon as it was published. This book came out in 2002, and so there are literally hundreds of paperweights that aren't included.
However, it has a beautiful illustration of each paperweight, and gives details of the design, the dates of issue, the launch price, and a secondary value guide, which can be taken with a pinch of salt, given that it is now 4 years old. To gain a true picture of current secondary values you'd do better to study the prices that the paperweights fetch on eBay, where there are always hundreds up for bids.
That said until the publishers come up with a new edition, this is the best published guide available to collectors, and I wouldn't be without mine, and if you collect RCD paperweights you really need to have a copy.