I may be joining this discussion rather late but I do feel the need to respond to some of the comments made here. First, the point that DLS is boring, with overstrung plotlines from little foundations. Nevermind that this is an astonishing achievement in itself, but the devil is in the detail. Meticulously built-up and never irrelevant. True the pace is slow at times, but deliberately so, it makes you slow down when reading it, and savour the process.
Next, the supposed pretenciousness. Yes, maybe she is a little, particularly with the quotes she starts her chapters with or some of the assumptions she presumes her readers to go along with her on. But her audience at the time thought nothing strange of affected about this. It says someting more about our own generation's drawbacks in certain regards. And above all else, is not her erudition justified by her own deservingness of it - she put the work in, shame to waste the effort by hiding it.
The race relations business is rather vague and obscure in referances above, and is not something I recall taking away from the novels after reading them. I do recall someting about Jews and money-lenders but this is so common-place for the time that it is barely worth remarking on. Besides, when one comes to Sayers, one expects the dialogue to hold centre-place - if it is the characters having the discussions and making the disparaging comments, DLS is reprting them, not saying such things herself. Treat it as a document of the time.
The comments on her portrayal of women have already been answered.
She is not a whodunit writer but she never tries to be, setting out along a different path. The interest is in the means, or the motive, not the actual villain, who is usually obvious. This is a different kind of puzzle, and one often neglected by other writers. Celebrate the diversity!
Boy, did I go off on one there...