Best for mostLydia Davis · 2010
Lydia Davis's 2010 translation is the one I'd start with — famously precise, it comes closer than anyone to Flaubert's exact rhythm and ruthless clarity (he agonized over every word, and so does she). A few readers find it cool; that coolness is rather the point. This is where I'd start.
Most readableFrancis Steegmuller · 1957
Francis Steegmuller's 1957 version is the warm, freely flowing classic — the one many readers love best for sheer readability. Less literal than Davis, more novelistic. If you want to be swept along rather than admire the precision, start here.
Gustave FlaubertMadame Bovarytr. Eleanor Marx-Aveling
The free classicEleanor Marx-Aveling · 1886
Eleanor Marx-Aveling's 1886 translation — by Karl Marx's daughter — is out of copyright and free. Victorian and a little dated, but complete and historically fascinating. Free; fine for sampling.