Mérida is well covered by travel guides given its position as the main city of the Yucatán. For background on Maya history and culture, Michael D. Coe's "The Maya" is the standard introduction. John Lloyd Stephens' 19th-century "Incidents of Travel in Yucatan" (1843), with Frederick Catherwood's illustrations, is still readable and historically fascinating — it introduced the Maya ruins to the wider world. Amate Books (corner of Calle 60 and 49) has a good English-language selection on archaeology, Maya culture, and Yucatecan history.