If you are already a big fan of Patrick O'Brian's, and / or you prefer to always buy or at least read the complete works of an author rather than just the odd title, then I don't suppose there is anything anyone can say which would deter you from buying this, the complete Aubrey / Maturin series. However, in my opinion, I don't think it's quite worth it, from a readability point of view anyway (as for financially, then maybe more costs less, not sure in this instance.) Here's why I think this - moving straight into well cliched footballing pundits' parlance - It's a Game of two halves - very roughly so at least.
If you've already read at least some of the earlier titles (for those who haven't, it's ok, no spoilers here), then you'll have become very quickly familiar with the general framework and the spirit, and it is within this that each separate tale has its own variations, and this is the magic of the first ten books. There is a WYSIWYG Naval officer, Jack Aubrey - brilliant at sea, naive on land, strict but not a tyrant, and with his own not too honourable idea of the limits of fidelity; his friend and shipmate, Stephen Maturin - medico, naturalist and spy, and Roman Catholic, which definitely makes him the cheese to Jack's chalk. These two lead the way in each adventure, spread across the globe, lands as well as oceans, mostly set in the Napoleonic wars, but other wars and other colonial considerations are frequent concerns. But the stories are further enriched by several regular characters, some occasionals, and many one-offs. But the ones we all come to love are 'Preserved' Killick, the grasping, greedy, sly steward, yet ironically loyal to Jack and by extension his officers and friends, with his own captivating turn of phrase delivered with such rudeness, it is a source of great amusement to the reader. Barret Bonden, his long-serving, strong, loyal coxswain. Then there's three chaps who have been with Jack from their time as young midshipmen, Tom Pullings, William Mowett and William Babbington, and even when they've gone to other ships on sideways moves or promotion, they love to return to Jack, or even to assist him with their own ships, bolstering the show of force. There are others, including family, (as well as sweethearts in many ports), too many to mention really, but these characters show great love and loyalty to each other even when the chips are down. It is this familiarity which adds so much to the first ten books, but then ... it all dies off, and very sadly and at times very badly so. Mr O'Brian should really have stopped at 'Far Side of the World', and sat back and drank champers on the royalties, much deserved, especially for one so getting on in life.
After 'Far Side of the World', the framework is unknotted, a certain strangeness creeps in, and it's not the same. The series should really have ended at that point if Mr O'Brian's options had run out with regard to 'more of the same'. In fact, half way through the series the author himself, to sum up several points he made in an introduction, states that he had basically run out of war and, for some of the remainder asks us to suspend our sense of time and perhaps knowledge of the true events which, where possible, were used to give the stories a feeling of reality, and instead,accept the possibility of the year '1812B'. I understood this, in a way, but I think it would have been more honest to say 'I've run out of Jack'. By that I mean a Jack Aubrey still young and hungry and enthusiastic enough to carry on leading from the front. I think, and it's only a wild guess admittedly, but I think that Mr O'Brian came to regret starting the stories off with Jack Aubrey only at the tail-end of what could be called still young, and then, worse still, suddenly putting a huge lapse of time between two of the early books, the latter of which sees Jack older, and married with children. If he had bought himself more time by not doing this, then, there would have been 'more war' or in my opinion, 'more Jack' as well as Stephen and the others of course. But I suppose in 1969 he did not know he would still be writing about Jack and Stephen in 1999.
The second half / the final ten books are still readable, they are not dreadful, and there are some excellent bits here and there, especially involving a young lieutenant - William Reade - given charge of a spanking new tender which runs and races around Jack's ships, going on errands far and near, bussing officers to and fro between ships for dinner; you really do feel the young chap's glee when he is racing across the briny in this - the Ringle. But it is not enough, not in comparison with what went before, and on the whole, the series gets flatter and sadder, despite some heavy actions which make up these stories, and I was glad when I had finished the last book, purely because it had ran out of its own mojo, to paraphrase Cheryl Cole.
Finally, the following bothers many but equally, many others are just mildly amused. How the perceived final MSs - from purely an editing / continuity point of view - were ever passed is a mystery. There is one persistent error on a sailor's name - you get Davis or Davies all through the series. Then, although the dialogue whoever it's from covers the necessaries, there are at least two sections of dialogue which do not go back and forth logically, and ends up with one person talking to himself, but through author error, not through the usual sense of the phrase. Later on in the series, the author brings back to life two characters who had died at sea well before, but they do not prove any problem as far as the story goes. And finally, this is purely style as far as some readers and reviewers are concerned, but considered sloppy by others. Patrick O'Brian liked to cram more into a paragraph than is considered convention, with the end result being sudden changes of sets of characters, emphasis, and even totally different situations. But, although these things should be pointed out, they don't really bother me as such.
All in all, the first ten books is what it is all about, the rest is, in Beatles terms, Let it be in comparison with Sergeant Pepper.