Ive felt that boredom much more than once, still havent in poker tho, but in other games I certainly have. In some point of the game you just show no interest in playing, youre distracted, not careful. Usually it is okay, but to be that person in poker costs you. I guess you can get that over with if you earn some money by it. You can read articles in Pokerschool, look for gripsed on youtube, his videos has been proven to be useful, atleast for me. And for books is relative, it depends what game you would like to play.
Also learn to calculate your odds
and outs, if you already havent. Its hard to propose something to you since you have 1200 posts. Maybe you could guide us which parts of your game sucks and which not.