SAT...room for improvement?

Hey, so I got my SAT scores today (first time taking it) and I am extrememly disappointed. From the first time I took the PSAT, my score has increased by about 40 (1st time PSAT-140ish, 1st time SAT-1800ish). I have a few prep books that I've gone through thoroughly. Is it possible for me to increase my score to about 2100? How much work will it take? Have you increased your SAT score by about 200 points before? I'm pretty much an average student. Thanks.