I've never heard of "Barddas". What's that about?
I've heard wonderful things about LeGuin but have yet to give her a proper read. How do you like her?
"Barddas" is Iolo Morganwg's exposition of Bardism/Druidry -- a very interesting text, IMO, and a pretty fundamental one in connection to the revival/continuation of the Welsh Bardic tradtion.
As for LeGuin, I've mainly read short stories and fantasy by her so far, rather than her SF works (which are on the list). I like her stuff a lot, especially for the Taoist influences interwoven.