Do you have any particular way of reading? Like just read the same book in your spare time, or flip between books as long as they hold your interest? Or even a way of choosing which books to read?
Most of the time, I flip between two books. The trick is to pick books that complement each other. Like say maths and machine learning, or a book on JavaScript and a JS framework. I usually read on the mornings & weekends and then spend an hour or two doing the exercises/projects at night, after work.