Complex sentence: Marguerite left the Bahá'í book The Dawn-Breakers out for him to read-after picking it up and setting it aside once, he read it three times in three weeks and by December 1939 was avowedly a Bahá'í officially joining the religion in 1940.
Split into simpler sentences: Marguerite left the Bahá'í book The Dawn-Breakers out for him to read. After picking it up and setting it aside once, he read it three times in three weeks and by December 1939 was avowedly a Bahá'í, officially joining the religion in 1940.