I guess I’m going to have to be the one to do it: Because they are cur-tailed. 
I saw the movie first, then gobbled all the books in one titanic (hah) read. I loved the movie, and I like very much the actor who portrayed Stephen, but admit he didn’t jibe too well with the way the character was portrayed in the book. That actor also did a good job as John Nash’s college roommate (snicker) in A Beautiful Mind. He works well with Russell Crowe.
Nifty factoid, for those who watched the RSC’s glorious version of Nicholas Nickleby: Preserved Killick was portrayed by the same actor who played Smike in NN. He’s one hell of a character actor.
See, that’s the funny part. I am interested in history, and generally enjoy strong well defined characters. I WANT to like the book series but so far I haven’t liked it as much as I liked the movie.
But I realize I can’t fairly judge a series of that length by one book, so I intend to try at least one more, if not a couple.
Did you start with Master and Commander? I suggest reading them in order.
MAC is a naval adventure yarn based on Cochrane and the Speedy. As the books progress the characters and the relationships develop and O’Brian goes from just adventure to the interesting mix of adventure, social and natural history and relationships.
There is a book on recipes from the books (spotted dog and drowned baby come to mind), there is a book A Sea of Words on the nautical terms used.
Anyway, my point being that as he first wrote an adventure novel and became more complex, you can read them in order and start out simply.
Give you joy, Sir! 
Yes, I started with the first one. I will probably continue in order. I’m the kind of person who can’t stand coming in on the middle of a movie, or a miniseries: I need things in the “proper” order.
Some of my favorite bits are when Stephen tries to explain nautical matters to guests who are even more ignorant than he is.
From The Mauritus Command:
Stephen: “Pray explain this new and splendid rank of yours.”
Jack: “Stephen, if I tell you, will you attend?”
Stephen: “Yes, sir.”
Jack: “I have told you a great deal about the Navy before this, and you have not attended. Only yesterday I heard you give Farquhar a very whimsical account of the difference between the halfdeck and the quarterdeck…”
Sometimes when I am reading Stephen’s explanation of something nautical, I am sure there is something hilariously wrong about it but I can’t catch what it is.
I happened to see this movie for the first time three days ago. I really liked it. Reading this thread, I can see that to have the other ship be American instead of French would really make more sense. I am definitely interested in reading the books, though I know next to nothing about seamanship or the English, French or American navies of the period.
It was exciting and poignant without being over the top as so many hollywood movies are. I loved the parts where they look at the design of the other ship, devise a method of attack, and practice until they’ve perfected their technique. I liked the doctor as a misfit with both wildly wrong ideas and dead-on right ideas. I thought the boy whose arm was amputated did a fantastic job of being believable at being heroic. I was fascinated by the captain’s determination to capture the other ship to the point of exceeding orders and sacrificing much else to do so. I loved the battle scenes. I would definitely recommend this movie.
I actually have never warmed to the books, despite being a fan of Hornblower. I’m not sure why. Something about O’Brian’s prose style I suspect. But I enjoyed the movie immensely.
The American / French switch actually annoyed me for a bit while I was watching the film, although not having read the novel I didn’t know the switch had been made until I looked the movie up on IMDB later.
There’s a scene where the officers are gathered in the wardroom and they ask Jack to tell a story about serving under Nelson. As I was watching it, I thought that the attitude of the officers seemed all wrong – they had this awestruck, worshipful attitude toward Nelson that seemed out of place considering that the movie took place right around the time of Trafalgar when Nelson would have very much been a living presence in the Royal Navy. He would have been feared, respected and admired in 1805, but not worshipped. It was the one false note in the film and I actually ranted about it a little to my wife afterwards.
Of course I found out later what the problem was. The novel is set in 1812, not 1805. Seven years is PLENTY of time for a MAN to turn into a GOD. The scene had been written as though Nelson were long dead, as he was in the original story, and was never changed to take account of the shift in dates!
Come now, Sir.
Who would you serve under, Hornblower who would attack the entire French fleet with a single fireship and those damn’d pistols his wife bought him, or Lucky Jack Aubrey, who, in the horrible old Leopard fleeing that big Dutchman in an arctic storm, threw the guns overboard and had begun starting the water?
Historically false or not, in the books, Aubrey has that extremely worshipful attitude from beginning to end. It arose from his having served under Nelson early on in his career. And, of course, Nelson once asked Aubrey to pass him the salt at dinner, IIRC.
Indeed, Sir, you are correct.