、。
Really? This is a surprise.
Literal
True-[question-か], this [topic-は] surprise [is-だ].
Two clauses loosely joined. 本当か is the plain-form question ('really?') — somewhat masculine. 驚き is the noun form of the verb 驚く ('to be surprised'), a common derivation where a verb's masu-stem is used as a noun. The two clauses are simply juxtaposed without a connector, a casual conversational pattern.