chess skill
This site allows you to play more to try things and practice what you know and to look over your games more easily, so it will help you improve. Chess books provide you with a wealth of insight and much deeper reviews of games from very skilled players.
The answer to your question is "yes, but using both will help even more".
This site has all sorts of benefits for you.
You can also become a stronger player by recognizing your mistakes and then trying to not make the same mistake over and over again.
Good luck! [or I should say good skill!]