astonishing; amazing; surprising
A fixed prenominal expression (連体詞) meaning 'astonishing' or 'surprising'. It is used before nouns to express that something is remarkable or unexpected. It can carry a positive nuance like 'wonderful' depending on context.
He solved the problem with astonishing speed.
This museum has many amazing works of art.
驚くべき means 'astonishing' and can be positive or neutral, while 衝撃的 usually implies a stronger, unsettling or distressing shock.
驚くべき is an adjective meaning 'surprising' that directly modifies a noun (驚くべき事実), while 驚くほど is an adverb meaning 'to a surprising degree' that modifies a verb or adjective.
Derived from the verb 驚く (to be surprised) + the classical auxiliary べき (should/ought to), which functions as a fixed prenominal modifier meaning 'that should surprise one' → 'astonishing'.