Enterprise AI Maturity is a practical handbook for assessing and advancing enterprise AI capability through the EAIMS open framework. The 64-page first edition presents eight maturity dimensions, five maturity levels, evidence-confidence scoring, risk-sensitive gate conditions, a 90-day acceleration plan, and a practical six-stage assessment workflow. Fourteen chapters and ten appendices provide a 64-indicator assessment instrument, five-level capability anchors, an evidence register, a minimum evidence pack, an assessment workshop playbook, an AI system inventory template, an AI impact assessment canvas, a responsibility assignment guide, a glossary, and an external alignment map. EAIMS is an independent improvement framework and does not by itself confer certification, regulatory approval, or legal compliance.