It's never too late!
My advice if you really want to improve your game is study tactics/combinations and all kinds of checkmates again and again and again until you dream about them in your sleep studying tactics seriously for about 11 months will not only make you a better chess player but a deadly tactician!
http://www.amazon.com/How-Become-Deadly-Chess-Tactician/dp/1901983595
http://www.amazon.com/Complete-Chess-Workout-puzzles-Everyman/dp/1857445325/ref=sr_1_1?ie=UTF8&s=books&qid=1269208957&sr=1-1
http://www.amazon.com/Chess-Tactics-Champions-step-step/dp/081293671X/ref=sr_1_1?ie=UTF8&s=books&qid=1269208990&sr=1-1
http://www.amazon.com/Tactics-Tournament-Player-Comprehensive-Course/dp/1889323020
http://www.amazon.com/Chess-5334-Problems-Combinations-Games/dp/1579125549/ref=sr_1_1?ie=UTF8&s=books&qid=1269209190&sr=1-1
http://www.amazon.com/Simple-Checkmates-J-Gilliam/dp/034540307X/ref=sr_1_1?ie=UTF8&s=books&qid=1269209256&sr=1-1
http://www.amazon.com/Brilliant-Checkmate-Chess-lovers-library/dp/0879801107/ref=sr_1_1?ie=UTF8&s=books&qid=1269209287&sr=1-1
Not an exhaustive list but they are the best books I know of on tactics!
It's important to also study system if you want to be a serious Chess Player:
http://www.amazon.com/Game-Chess-Algebraic-Siegbert-Tarrasch/dp/1880673940
http://www.amazon.com/Laskers-Manual-Chess-Emanuel-Lasker/dp/188869050X/ref=sr_1_1?ie=UTF8&s=books&qid=1269209485&sr=1-1
http://www.amazon.com/System-Chess-Classics-Aron-Nimzowitsch/dp/9197600539/ref=sr_1_1?ie=UTF8&s=books&qid=1269209509&sr=1-1
Books and lessons from experts are only part of the answer of becoming better you must also seek out and play human opponents (computers are ok for sparring but they don't fight like people do it's not the same) who are better than you in slow games as often as you can opponents who can crush you badly and give you a very bloody nose are the best teachers at the board they'll play hard against you every game you'll get the sort of practice and experience that you need in order to become a respectable and deadly player yourself with time and hard work.
Good luck!
Edit:
I agree with the poster who said join a real club online is a waste of time because too many people cheat with chess engines and they use low tactics like letting their time burn to frustrate their opponents.