This one is very usefull:
Chess Opening Essentials: The Complete 1.e4
Ruben Fine's book "The Ideas Behind the Chess Openings."
It goes into the theory and isn't too heavy. It helps you understand some of the main theoretical lines behind the major openings.
In my opinion, no. You should learn the basic principles behind the openings and try to apply them in each and every game. I second the recommendation of "Ideas Behind the Chess Openings" - excellent book to start learning about opening play.
I have had good use of "King's Gambit fro the creative attacker" by my countryman Thomas Johnsson. I think Quality chess books are about to release a new book on KG
I have looked at my overall game and have found my main weakness is the opening game. Does anyone have any suggestion on what book I should get to read and study. What other ideas are out there for improving this part of my game.