Whatever sails your boat really. If you are someone who is comfortable with reading e-books and marking and making notes simultaneously, feel free to read it online, however if you are old school and need the book in your hand and a pen and paper to study effectively, buy the books. The point is to be thorough with the content, whatever way you choose to do that, is your call.
BONUS: We have made a list of 50 of the 50 greatest e-books ever, so you can check it out! You can view some excerpts from the book here:.