I am rated 1845. Was rated 1539 half a year ago.

At this level 1845, what is important to study?

What is important to learn?

Looking forward to the debate?

:-)

Just keep using tactics trainer and chess mentor. Here are some books I'd recommend and that I am using atm if you want to study books:

Endgame: http://www.amazon.com/Capablancas-Best-Chess-Endings-Complete/dp/0486242498

Strategy: http://www.amazon.com/Simple-Chess-Everyman-John-Emms/dp/1857442385/ref=sr_1_2?s=books&ie=UTF8&qid=1343255883&sr=1-2&keywords=simple+chess

Game collection: http://www.amazon.com/Mammoth-Worlds-Greatest-Chess-Games/dp/0762439955/ref=sr_1_3?s=books&ie=UTF8&qid=1343255951&sr=1-3&keywords=The+mammoth+book+of+chess

Tactics: http://www.amazon.com/Improve-Your-Chess-Tactics-Practical/dp/9056913344/ref=pd_cp_b_1

Cool. Thanks a lot. :-)

At this level improvement becomes more difficult. You may want to try coaching, with someone rated 2200+ to help you.