The SoT series IS about Richard & Kahlan! Without being interested in those two characters it's just pointless reading the series. Again you could just search for Cara, Berdine and Raina on the wiki and learn almost everything there's to know about them.
It's the depth of Richard and Kahlan's personalities, their lovestory, their interacting with other people and creatures, their struggle throughout the series the whole storyline revolves around! Nicci does become important for a while to fill the place left empty by Kahlan's absence, but the impact on the story the three mentioned Mord'Sith have is quite little in the grand scheme of things.
Yes, I did like them too, especially Cara, but I wouldn't struggle through 7.301 pages just for a few funny lines from her which I, mostly, could also read in a thread here on this very board.
Reading the SoT series just for Cara, Berdina or Raina is like Reading
Harry Potter for Dobby, or
Lord of the Rings for Eowyn. Nobody would do that.
