Inclusive design considers the full range of human diversity from the start of a project, not at the end. Microsoft's Inclusive Design toolkit frames it as solving for 'mismatched human interactions': the moments an environment fails a person. Inclusive design and accessibility overlap but aren't the same. Accessibility is specifically about disability and the standards that support disabled people. Inclusive design is broader: disability, language, age, culture, and situational limits (holding a baby, using a phone in sunlight, on a slow connection).
Kat Holmes' Mismatch is the standard introduction. It centres three ideas: recognise exclusion, learn from the people a design excludes, and solve for one to extend to many. The curb-cut effect (kerbs designed for wheelchair users that also help prams, luggage, and cyclists) is the canonical example. Worth handling carefully though: the wider benefit is real, but it isn't why curb cuts exist. Disabled people's access is the point.
Include disabled people in research from the start, not as a separate 'accessibility test'. Co-design with people rather than designing for them. Treat accessibility as a baseline, and be honest that designing for everyone isn't achievable. The goal is designing for a wider range of people than the default.