This is not a publication I’ve seen before so it may new or it may be slightly older but either way it looks to be a handy guide to investigative journalism.
The http://www.investigative-journalism-africa.info/ is backed by the Konrad-Adenauer-Stiftung foundation and falls somewhere between a teaching tool and a manual. The individual chapters are available online for free so little reason not to take a look.
For more journalism publications take a look at the Media Hack Resources page.