When you are about to read a hard book , remove the intention that it is hard to you. When you are preparing for exams with the hi-tech books which you say as a hard books segregate the topics , understand the theme and try to build the answer in your own style with the good understanding of the concept.

First I Congratulate you for the habit because nowadays book reading is hardly found among youngsters. Reading Book is not that hard. Tips that you can follow:-
->Select a spot where you feel comfort and calm
->Keep a Dictionary with you and refer it while reading
->Go through the table of contents which gives idea about the book
->Read the entire book even if is boring so that you may come up with better sense of book.