I really recommend Mars (1992), by Ben Bova. It has sequels and I didn't care for the second anywhere near as much (still okay) but the first was great.
Greg Bear's Moving Mars (1993) is also excellent.
Joe Haldeman's Marsbound (2008) has a couple of significant problems and its sequels also aren't so good, but it also has some excellences.
Allan Steele's Labyrinth of Night (1992) is "A Novel of Mars." It isn't his very best, but it's decent.
I haven't even read Geoffrey Landis' Mars Crossing (2000) but it is in the Pile and I have read many superb stories by him and have heard good things about the novel, so I feel pretty confident (hopeful, at least) about it.
One of the more famous and popular ones is the Mars trilogy, beginning with Red Mars (1992), by Kim Stanley Robinson but I don't care for them. Red Mars was the best of the set, though.
An outlier both in time and perhaps main focus is Frederik Pohl's Man Plus (1976) but it's a book I recall very favorably about adapting a man for life on Mars. It does deal with our modern conception of Mars, at least, vs. the Bradbury/Brackett/etc. Old Mars.