Understanding AP, AR, GL in details

Hello All,
I have been a developer in AX 2012 since a year now.
I have a very good knowledge of HR, Proj. Mgmt and accounting but now I I have started to work on Acct.payable, Acct. receivables, sales, purchases, manufacturing modules…lot of new stuff and lot to learn…‏

Can anyone tell me which will be best resource i.e. where I can read/learn and get up to speed with these financials tables, relations, classes to understand these modules in a faster and quicker way?
Thanks in advance.
Shankar Iyer