Complex sentence: Book III of the General Theory is given over to the propensity to consume, which is introduced in Chapters 8 and 9 as the desired level of expenditure on consumption (for an individual or aggregated over an economy).
Split into simpler sentences: Book III of the General Theory is given over to the propensity to consume. The propensity to consume is introduced in Chapters 8 and 9 as the desired level of expenditure on consumption (for an individual or aggregated over an economy).