Molecular genetics textbook (free?) suggestion for first time
I can’t comment otherwise this would be a comment, not an answer, sorry... 

If you can’t lay your hands on a cheap (legal) text book that is of quality and in digital format then  maybe check out course material from MIT open courseware or something similar. As a further alternative, you should be able to find decent pop science books which are applicable and may be more useful than you think. The Epigenetics Revolution, for example, provided me with a really solid grounding when first trying get to grips with the subject.