I have to say that I was a bit disappointed in this product. There isn't a great deal of meat on the bone here.
On the plus side, There is some good background information here that might be quite important if you run a pirate heavy campaign. The art is good and some of the table information is useful.
On the negative side I have to say that there is little here regarding ships, how to use them, not much for spells or sea-based items.
I would have to say that there is enough to make the product useful in some ways, but I would probably call it "Piratres at a glance".
Suppliment this book with (if you can find them) "The Seafarer's Handbook", "Pirates!", "Arms and Armor 3.5" (for special item creation)and applicable parts of "Swashbuckling" series.
To be fair, it's hard to get pirates into a mixed world without butchering the whole concept. Your DM is faced with a bit of a challenge when working with pirates, but it can be a fun addition.