The Commodore (Aubrey/Maturin Series): Book 17

The 18th Century heroes, Captain Jack Aubrey and Dr. Stephen Maturin of the Royal Navy, are sent to the fever-ridden Gulf of Guinea to disrupt the slave trade. But their ultimate destination is Ireland where the French are mounting an invasion, a mission that will test Aubrey's seamanship and Maturin's talents as a secret agent. By the author of The Wine-Dark Sea.