"He did see a good book."
Translation:Mi wnaeth e weld llyfr da.
Should iawn allso be acceptable at the end? I'm sure ive seen it be used for good before.
It can be use when describing yourself as in "Dwi'n iawn diolch"="I'm good/fine thanks" but it wouldn't be used for nouns, but you could add iawn to the end of this sentence to make it "He did see a very good book".