The adjusted close price incorporates adjusted figures for dividends and any splits. So current adjusted close divided by historic adjusted close provides an indication of total gains (accumulation) as though dividends had been reinvested.
Its all just a guide however, as reinvestment of dividends is subjective. In practice typically the share price will drop by the dividend value amount on the x-div day, but you wont receive that dividend for 6 weeks or so until after that date, by which time the share price will have moved.