These two novels were published in 2001 and 2004 respectively. 'Saucer' is set in the present day and describes what happens when a perfectly preserved - and fully functional - flying saucer is discovered in the Sahara, embedded in rock sediments 140,000 years old. The hero of the story, Rip Cantrell, is a young researcher who makes the find. With the aid of a former US Air Force test pilot Charlotte "Charley" Pine, he steals the saucer out from under the noses of various groups who arrive to claim it. What follows is an exciting contest as various governmental and private organisations battle to claim the prize.
'Saucer: The Conquest' takes up the story a year later. We are evidently in a slightly different parallel universe, in which the French government is manning and supplying the only base on the Moon. A wealthy French entrepreneur is funding much of the project, but he has a secret agenda: a saucer-derived anti-gravity weapon at the Moonbase which is capable of wreaking limitless destruction on Earth, and which he intends to use to rule the world. Charley Pine has taken a job as pilot on one of the French 'space shuttles' and of course becomes involved in battling the threat, as does Rip Cantrell. A series of space and aerial combats involving saucer beam weapons takes place before the finale.
Coonts is a writer of light adventure techno-thrillers rather than science fiction, and these books are very much in that mould. 'Saucer' is the more successful work, in my view, because there is only the one "MacGuffin" - the saucer itself - and the novel is otherwise very much a contemporary all-action story. It's an easy, undemanding read and the author is a good enough story-teller to keep the pages turning.
'The Conquest' takes a sharp step towards the more fantastical James Bond films - I kept expecting the villain to start stroking a fluffy white cat - and therefore requires a more strenuous suspension of disbelief. I was initially unimpressed, but Coonts' story-telling powers eventually won out and I carried on to the end.
Neither book advances the state of the art - indeed, they could have been written decades ago - but they're an entertaining way of passing the time if you need a break from more serious SF. This particular series may not yet be at an end, because there's a hook at the end of 'The Conquest' which suggests that a third volume may well be along sometime.