Two strong starting points were recommended:

• Henri Cartier-Bresson: The Man, The Image & The World — suggested as a great overview with large, high-quality reproductions and a comprehensive selection of images.
• Henri Cartier-Bresson: The Modern Century — another good option, published to accompany the MoMA exhibition of the same name.

If your priority is seeing a broad range of his photographs, either should work well as an introduction. Based on the feedback, The Man, The Image & The World sounds especially well suited if you want a substantial visual overview rather than a text-heavy book.