As in Aeschylus (as I recall--it's been awhile), Clytemnestra definitely has the best of it for most of Seneca's Agamemnon; Agamemnon himself is even less of a presence than in Aeschylus, showing up for a few lines of wind-baggery (allusion intended). She gets the most philosophically deep lines and the back story grants her sympathy. Thus, it's all the more shocking when Electra shows up and suddenly gives us a completely different point of view, and Clytemnestra forfeits all sympathy. Seneca isn't usually given much credit as a dramatist, but this shift in perspective works very well and is as shocking as it clearly is intended to be.

Now I'm on to Thyestes, which opens with a prologue spoken by, guess what, a ghost.