I skimmed lippencott (they have figures that highlight genetic/metabolic disorders and biochemical pathways summaries that I found easier than reading the book cover to cover). I also read the pathophysiology underground clinical vignette series which highlighted the most common metabolic genetic disorders, and did q-bank and first aid for hy. Didn't waste my time memorizing krebs/glycolysis/etc, but did try to remember key enzymes and their regulators from aforementioned pathways, and disorders that are linked to them.