The documents released today in English did not include the complete 600-page report. They did release an executive summary, some appendices, and an introduction document.
National Diet: The Fukushima Nuclear Accident Independent Investigation Commission
Executive Summary NAIIC_report_lo_res
Workers Survey workers_survey
Evacuee Survey evacuees_survey
Commission Meetings commission_meetings_low_res
Our archive of the Diet investigation can be found here.
Prime Minister’s Office: Investigation Committee on the Accident at Fukushima Nuclear Power Stations of Tokyo Electric Power Company
Final report: https://www.cas.go.jp/jp/seisaku/icanps/eng/final-report.html
Initiation document https://web.archive.org/web/20120312121831/http://icanps.go.jp/eng/2011/07/05/0524CabinetDicision.pdf