|Java is a programming language. Object Orientated Programming is a programming method. I wouldn't worry too much about OOP to begin with unless you are going to learn programming. OOP is an advanced concept that you move onto once you have mastered the basics of computer programming,|
IT covers such a wide spectrum if disciplines and skills that there is no single book that covers the basics. You need to decide which branch of IT you wish to pursue; programming, data processing, networking, hardware, the list is endless.
Probably the first place to start is to learn a little about hardware, how a computer works and what all the different devices do. In doing so you will touch on all aspects of IT then you can decide which branch interests you. Nobody is an expert in all aspects of IT.
You could start here. There is a wealth of knowledge on the Internet.