I tried to get Massie's other WWI book, Dreadnaught, but sadly all the library had was _Castles_. Dreadnaught is about the pre-war naval design and procurement process (exciting!), while _Castles_ is about the actual fighting of the naval war (meh). _Castles_ is straight forward, knowledgeable, and readable, and covers the naval action in extensive but understandable detail. The main flaw of the book is that it has too much padding, especially at the start. For instance, rather than just saying that something happened at the Dardanelles, Massie has a full paragraph describing the Greek myths about the Dardanelles and its place in ancient naval history and so on. I could have done without the extra flavor text, and I don't feel that I missed much by only skimming several of these sections.
I can't say that the book was a revelation; it mostly accords with the standard story of the naval war. You have a few indecisive naval engagements leading up to Jutland, a disaster or three at Gallipoli, the indecisive main battle at Jutland, and then the German navy spends the rest of the war at harbor. After that the uBoats come into play and narrowly fail at cutting British supply lines. In battle, the tactics were sound for both sides. The major mistakes were due to various miscommunications and failure to share information.
*Gefechtskehrtwendung! This is the German command for a special maneuver where every ship in the fleet does a 180 at the same instant. The maneuver saved their fleet twice at Jutland. The British fleet had no similar maneuver, and at key points had trouble sailing together in straight lines.
*The aptly named Commander Goodenough, who did an alright job, and made several mistakes, but never messed up so badly as to get himself fired/killed.
* The pairing of Beatty and Jellico, a sort of Zap Branigan/Kif Kroker duo. Beatty gets the best quote of the book award. After sending some incorrect signals, he accidentally separates his battle cruisers (glass cannons with high range & speed which are meant for kiting) from his dreadnaughts (slightly slower, but much more heavily armed and armored). He then sails his battlecruisers at the enemy fleet and waits until he is within range of their guns before opening fire himself. After just a few minutes of combat, a third of Beatty's battlecruisers have exploded into giant fireballs, prompting him to say: "What ho! There seems to be something wrong with our bloody ships today."
National stereotypes are generally upheld. The British come across as affable bunglers with a sort of innate diplomatic sense. The Germans are very precise and efficient, with great forecasting and training, but also batshit crazy at a very fundamental level.