Spoilers ahead. I'm on the next book now so my memory is a bit hazy regarding the specifics or the quality of the writing.
Summary/spoilers:
Ramage is given orders to root out privateers in the Spanish Main and is also given the schooner La Creole as a tender with Lt. Lacey as commander to do this job. As per the description at the beginning they interrupt a privateer attacking a merchantmen. By the time they get close enough to board the privateer has escaped by they found that everyone on board has been murdered.
Next, they are able to capture the French frigate La Perle using subterfuge by tricking their captain to come aboard, then they just board the leaderless frigate and compel the lieutenants to surrender in the confusion. However they find that the La Perle has been badly maintained and is sinking by itself. He sends the frigate off to ground itself on a remote Spanish coast with Lacey following because he did not want 300+ French prisoners.
In the second half of the story he visits the Dutch island of Curacao where 10 privateers are hiding in the port. The Dutch have been taken over by the French and are uneasy allies of them. As the Dutch governor of the island says, he has 3 choices, he either goes over to the British, wholeheartedly supports the new regime or pretends to support the new regime so that the French don't put a real gung-ho republican governor on the island. But in reality he (van Someran) is a realist and looks after himself first.
Van Someran is actually in dire straits because the French privateers have been refused credit by the Dutch tradesmen. Not having supplies and the ability to sail, they have decided to ravage the island instead. Numbering 350 men, they are joined by 150 Dutch rebels. Since van S. only has about 100 troops, he decides to surrender the island to Ramage after explaining his situation.
Ramage accepts the surrender and strips his ship of men to attack the rampaging mob. He defeats them after a couple of days of action. When he goes back to the port, he finds that a Dutch frigate has arrived from the Netherlands and van S. goes back on his word daring Ramage to fight the frigate and the guns of the fort. Ramage doesn't waste any time and that night fills one of the privateers with powder, sails it next to the Dutch frigate and explodes it destroying it. Van S. is taken prisoner and sent to Barbados.
The surrender of Curacao to the British (a Captain Watkins) was based on a real incident and is referenced to in the postscript. However, the wikipedia entry of the same event directly contradicts it. The wiki entry paints Watkins as the one who goes back on his word. According to the wiki, French forces were invading the island and 2 American frigates were sent to protect American interests (ships and specie). Watkins was also there to fight the French. He teamed up with the Americans to defeat the French. However after the French defeat, Watkins seized the American property instead of protecting it and releasing the ships. The British government was not happy with his actions and cashiered him and returned the goods when his new commander arrived from Britain.
Overall the book is not bad. There is a lot of action, though Ramage's streak of wins on easy mode is sometimes a bit laughable. As usual, there is a lot of Ramage worship from everyone he meets, dialog filler from the crew, repeat hashes of the beautiful Marchesa and past events.
To be honest I'm reading the books now to finish the series, not because it's a great series. There is a huge difference between Hornblower and this series. CSF is a greatly talented writer, better in many times of magnitude. I can see that Pope tries, but he just isn't on the same level. Another thing with CSF is that you can see his writing improve from the first book to the last one. With Pope, it stays roughly at the same level, which is better than Stockwin and Lambdin, whose writing got worse and I abandoned those 2 series before I finished them.