I've been doing sudoku for several months now and found it addictive. I've enjoyed discovering "if this, then that must ..." strategies but have reached a level where I need to better understand different strategies for aspects such as the level after the obvious and secondary eliminations early in a soduku. Oddly enough, I have managed to finish puzzles tabbed as "most difficult" and have struggled with ones termed "moderate," so I figure that reflects how one's mindset matches that of the creator of the puzzle.
I turned to Sudoku for Dummies and found it fairly useless as it ends its instruction at what seems to be a good starting point. I have followed some of the threads here and realize I am waaaaay below the level of folks there, but want to progress. I have no desire to use software that fills in a puzzle because without the explanation of why something went where, I learn nothing. Can anyone provide links of articles that explain medium-level or advanced strategies in a manner that makes them feasible to follow? Or, is there a particular book that goes into comprehensive explanations?
Any help would be much appreciated.