Complex sentence: The first novel Lethem began after returning to New York City was "Motherless Brooklyn", a return to the detective theme, this time maintaining objective realism while exploring subjective alterity through Lionel Essrog.
Split into simpler sentences: The first novel Lethem began after returning to New York City was "Motherless Brooklyn", a return to the detective theme. He maintained objective realism while exploring subjective alterity through Lionel Essrog.