By "openings" do you mean the relationship between one day's close and the next day's open? Or do you mean how to trade off the first N minutes of price action?
If you're interested in the first concept, you want books on trading gaps; if the second concept, you want books on price action.
I've never studied gaps in detail, though I've traded off them using basic price action concepts.
I've studied intraday price action concepts thoroughly and I recommend Al Brooks (I've heard his more recent three-volume set is easier to read than his first book), and Bob Volman's Forex Price Action Scalping. Don't worry about the Forex and 70-tick chart parts of it; the concepts are superb and you can apply them to the 1-min chart on almost any liquid instrument during regular trading hours.