This seems to have fallen off the ledger site: the latest ledger manual in easily-browsable form. To be clear, this documents the mature ledger, not the young hledger released yesterday. But it's a good read, gives the big picture and some of it is directly applicable to hledger.
one big page: http://joyful.com/repos/ledger/doc/ledger.html many pages: http://joyful.com/repos/ledger/doc/ledger/ pdf: http://joyful.com/repos/ledger/doc/ledger.pdf
