Reddit mentions of Be A PMP Ace In 30 Days: How I aced the PMP Exam in one attempt, without taking a break from work and how you could do it too! (PMP Ace Series Book 1)

I needed exactly 34 days of prep (that does not include the time I took for accumulating the 35 PDUs and a weekend I lost due to an unexpected travel). Prepared about 3-4 hours everyday on weekdays and a couple of hours more on weekends. I know a friend who did it in just under a month but he thinks he just scraped through. You need to have a good plan to keep a schedule (you can check this Kindle Book - I followed the same - older version then).

My opinion is that for practicing project managers who have fair exposure to actual project management, a good command of English, an aptitude to learn and grasp concepts quick enough, and some discipline, 150-200 hours is enough and 1-1.5 months is sufficient overall to crack the exam. I'm not personally aware of anybody who prepared and did it in less than a month, and I really don't think most people need more than 2 months on an average, if that person can prepare about 3 hours daily without fail.