Speaking as a photographer and a collector/dealer of erotica, what's interesting about Dolan's Pink Pussy series (this is the third book of three so far) is more than just the subject matter - which can be found abundantly on the web - it's the high quality and professionalism in these books, far above most web content, as well as the fact that they were the first of this focused genre to hit the market.
After Dolan's first Pink Pussy book became a surprise best seller (in spite of the almost comically blatant title), all the other publishers jumped on the bandwagon and rushed to market with a number of rather pale collections of second rate stock shots. You may still find them on the web (and you can still find their trolls making negative comments here) but the only superior quality monographs remain these Dolan books, which are also popular in actual brick and mortar bookstores in Europe.
However, I don't see this trend lasting very long, given the increasing price of publishing and the advent of more and more ebook devices, so I think anyone interested in published erotica (real books) will want to add this series to their collections. Over the next few years it's likely that most erotic content will be diverted to strictly digital media, so this kind of hardcover edition will be a rarity. I'd say in 5 or 10 years, it may be impossible to find any real books devoted to the work of a single erotic artist, and these titles may be going for many times their current price.