It doesn't matter. Just pick a topic that you are currently interested in and start reading. Go to amazon.com, type in the subject and find a book with the hi

It doesn't matter. Just pick a topic that you are currently interested in and start reading. Go to amazon.com, type in the subject and find a book with the highest ratings that sounds interesting. Sometimes I read about new languages I want to learn, sometimes about a tool I'm currently using but want to know more and sometimes just about programming in general.