How did Vladimir Nabokov’s early English novels differ from his major Russian novels?

Vladimir Nabokov’s early English novels, specifically The Real Life of Sebastian Knight (1941) and Bend Sinister (1947), are generally considered by critics to be inferior to his major Russian works, such as The Gift.1

While his Russian novels—including The Defense, Despair, and Invitation to a Beheading—established his reputation as a significant artist and master of unorthodox structure, his initial English-language prose did not reach the same level of acclaim. It was not until later works, such as Pale Fire, that Nabokov fully extended and completed the mastery of complex, unorthodox structure that he had first demonstrated in his Russian period.1