I don't think I can praise Barbara Rosenblat's voice talents highly enough. Each character is distinct and instantly recognizable. Male characters are very obviously male (HOW?) to the point I don't hear 'woman doing male voice' but 'male character'. She even AGES the voices, as the characters age (which they do through the Amelia Peabody series. One character in particular has gone from infancy to mid-thirties.) She's a little weak on some accents (Irish and American, for instance) but it only makes me giggle occasionally, not wince.)
But I don't think I can convey just how distinct each of the characters are. One or two words and I know exactly who is speaking - it's wonderful. But it did make me notice something: the "Master Criminal" started out with a voice so bland and non-descript I couldn't pin it to that character at all (which is EXCELLENT, considering the character. OMG!)
But later on... well, I sometimes think it's Ramses speaking, instead, and I can't help but think that's just as intentional, all things considered.