No the books aren't lying. The half-life of THC ranges from 0.8 days to 10 days. Many factors are involved in this from genetics, body fat percentage, metabolism, diet, physical activity, etc. Then you must figure smoking history (how much, quality, how often, etc). Some people can be clean in just a few days others who smoke many times daily may take 2 months to get clean. Consider yourself lucky. On the average though a daily smoker may take 20-30 days to get clean and a person who is completely clean and gets high one time can be clean in 5-7 days.