Moldova: A Romanian Province Under Russian Rule by Vladimir Socor — a concise political history of how this territory became a Soviet republic and then an independent state. Dense but useful background reading.
Wines of the Former Soviet States — if you are visiting primarily for the wine, this academic but accessible survey covers the Moldovan wine regions in some depth.
The Odessa File by Frederick Forsyth — set partly in Odessa, close enough to set the regional mood, and a good thriller for the train from Bucharest.
Eastern Europe on a Shoestring (Lonely Planet) — the regional guide covers Moldova with more practical detail than most. The Moldova-specific chapter is limited but useful for logistics.
Easter in Kishinev: Anatomy of a Pogrom by Edward H. Judge (isbn: 0814741932) — a careful historical account of the 1903 Chisinau pogrom, one of the most significant events in the city's modern history. Essential reading for understanding the Jewish community that once thrived here.
Studies in Moldovan: The History, Culture, Language and Contemporary Politics of the People of Moldova edited by Donald Leroy Dyer (isbn: 0880333510) — an academic collection covering language politics, ethnic identity, and post-Soviet transition. Dry in places but thorough.
Jewish Roots in Ukraine and Moldova by Miriam Weiner (isbn: 0965650812) — a guide to Jewish genealogical research with archival inventories. Useful for anyone tracing family history in the region.