The essential academic introduction is David Webster's The Fall of the Ancient Maya (2002), which uses Copán as its primary case study for understanding the Classic Maya collapse. Webster's fieldwork at Copán's Las Sepulturas zone provides the evidence base for much of the book. Readable and authoritative.
For a broader picture of the Maya world, Michael Coe's The Maya (now in its ninth edition) covers the archaeological background clearly. The chapter on Copán provides the context for understanding the site's significance. For the hieroglyphic writing specifically, Simon Martin and Nikolai Grube's Chronicle of the Maya Kings and Queens is the essential reference work — every named king at Copán is covered in detail, with the monumental evidence for their reigns.
For travel reading, Paul Theroux's The Old Patagonian Express passes through Honduras and captures the transport conditions of the 1970s; the Central American stretch is one of the book's best sections, though it predates the Copán archaeological zone's development as a tourist destination.