The Department of Justice Guide to the Freedom of Information Act, found here, is a valuable resource to both government employees processing and litigating FOIA matters and FOIA requesters. It is the definitive substantive position of the government on FOIA issues. However, not one of its sections has been updated since August of 2015 - some haven't been updated since 2009. If there had been no changes in FOIA that would be fine, however there has been legislation and a number of important Court decisions on FOIA matters since then.
While DOJ has given procedural advice on FOIA reporting consistently, it is unclear why there have been no changes in this important document. Hopefully, DOJ will remedy this in the near future.