Incidents of Travel in Yucatan by John Lloyd Stephens (1843) is the best starting point for anyone visiting the Yucatán Peninsula. Stephens, an American diplomat and explorer, travelled through the jungle with artist Frederick Catherwood in 1841–42, rediscovering dozens of Mayan ruins that had been swallowed by the forest for centuries. The writing is vivid, the enthusiasm genuine, and the drawings Catherwood made — published alongside the text — remain extraordinary. Isla Mujeres was one of Stephens's landing points; the context it gives for the Ixchel temple at Punta Sur alone is worth the read.
The Maya by Michael D. Coe is the standard modern introduction to Mayan civilisation — compact, clear, and updated in multiple editions as archaeology has progressed. Coe was a Yale professor who spent his career on Mesoamerican cultures, and the book manages to cover a civilisation that lasted three thousand years without becoming a textbook. Read it before you visit Punta Sur, Chichén Itzá, or any of the other sites in the region and you will see them entirely differently.
Cancún, Cozumel & the Yucatan in the Moon Travel Guides series doesn't quite fit the usual bill — it is a travel guide rather than a narrative — but Gary Chandler and Liza Prado's coverage of the Riviera Maya is detailed enough and opinionated enough to read as a companion rather than a directory. The sections on Isla Mujeres are honest about what the island is and is not, and the practical detail on ferry schedules, whale shark season, and the MUSA is well-maintained across editions.