Two beginner-friendly recommendations from the community are:

• Digital Macro Photography by Ross Hoddinott — recommended as a solid true-beginner book that covers the basics thoroughly. It may be too basic for advanced readers, but that makes it a good starting point.
• Closeups in Nature by John Shaw — an easy read that focuses on practical close-up techniques. Even though it isn’t centered on digital photography, the core macro concepts still apply, including lighting, subject-finding, and techniques like reversing lenses.

If you want a modern beginner introduction, Digital Macro Photography sounds like the best fit. If you also want classic fieldcraft and close-up technique, Closeups in Nature is another strong choice.