This book written after long Bear season. Lots of blue chips lost big percentage of it's gains. It is good to be reminded that how Bear season feeling is and keeping mind that there are such seasons.
Also idea of increasing and decreasing size of position and doing it with system is just fantastic. With some adjustments this can be used in bull market, or after big long crash, when stocks are trying to found their bottom then this system can become handy.
I read 2nd edition. I searched the differences between 3rd and 4th edition. I understand that in 3rd and 4rd edition, initial position is much larger(because writer see that in bull market larger initial position makes more money and season of market changed to bull market) but calculations are similar. I found 2nd edition is good enough for me.