I've been a fan of both Bernard Cornwell and Patrick O'Brian
for a number of years.
Both are known for their historic fiction set in the Napoleonic Wars.
Cornwell has written 20 books about Richard Sharpe,
a rough and ready British Army officer, up from the ranks.
Cornwell excels at writing battle scenes, capturing the
smells and sounds, the noise and confusion, the blood and the gore.
Some of them were turned into a TV miniseries in the mid-1990s,
with Sean Bean as Sharpe.
O'Brian wrote 20 novels about Captain Jack Aubrey and
Dr. Stephen Maturin of the Royal Navy.
The Russell Crowe movie
Master and Commander
was based on a couple of the books.
I recently finished the latest Sharpe book, Sharpe's Escape.
Near the end, there's an advertising section, which says
and The Economist proclaimed Bernard Cornwell,
"The direct heir to Patrick O'Brian."
Nonsense! They're both fine writers, in their own ways,
but O'Brian is a much better novelist than Cornwell.
The Sharpe books are fun, but formulaic.
Sharpe makes an enemy, usually an officer on his own side
or the other side; Sharpe is bloody-minded and stubborn;
Sharpe fights battles; Sharpe gets laid;
the enemy (usually) gets his comeuppance.
Thomas of Hookton (The Grail Quest series) is just
Sharpe with a longbow instead of a rifle.
Cornwell is capable of more ambitious work,
such as the Arthur books, but most of his writing
is simple adventure fiction.
There's plenty of adventure in the Aubrey-Maturin novels too,
but O'Brian is a much keener, more philosophical observer,
who brings depth to his characters.
Patrick O'Brian's naval mastery does a better job
of elaborating on this than I can.