According to the Klingon Wiki,

TKD describes the letter o as in "go or mosaic". This is confusing, because English speakers would do that with a diphthong, rhyming "go" with "glow" and saying "mosaic" like "mow-saic". This is not what Okrand intended. He just wanted to make clear that it's not o like in "cop" or "pot". The sound still is a clear "o" without a following u sound. The word qepHom should NOT rhyme with "home".

ORLY? Where does this revelation come from? TKD says that o sounds exactly the same as ow — meaning it's a diphthong that sounds exactly the same as American English go.