Complex sentence: He came to notice in 1912 when he published a book of poetry called "Scum o' the Earth" which looked at the class and monetary divide between middle class American and poor immigrants.
Split into simpler sentences: He came to notice in 1912 when he published a book of poetry named after a poem called "Scum o' the Earth". The poem had focussed attention on the monetary divide between middle class American and poor immigrants.