My answer: Is it strange that I'd want to recommend a 'good' one instead of a 'great' one? Of course, that would all be subjective, wouldn't it?! I think some of her novels are more accessible than others. (For example, some take three or four chapters to introduce--really introduce--the main characters.) I think I would recommend The Black Moth or These Old Shades or The Convenient Marriage.
I wouldn't recommend The Toll Gate.