There are a lot of Vietnam travel guides avaliable in the internet. To make your choice easier, here is a selection of the best books about Vietnam to help you during your journey.
Lonely Planet Vietnam (5th ed) - Mason Florence and Robert Storey
The Rough Guide to Vietnam (Rough Guides) - Mark Lewis, Jan Dodd
Vietnam and Angkor Wat (Eyewitness Travel Guides) - Richard Sterling
To Vietnam With Love. A Travel Guide for the Connoisseur. (To Asia with Love) - Kim Fay and Julie Fay Ashborn
Frommer's Vietnam: With Angkor Wat (Frommer's Complete) - Sherisse Pham
National Geographic Traveler: Vietnam, 2nd Edition - James Sullivan
Vietnam - Culture Smart!: the essential guide to customs & culture - Geoffrey Murray
Vietnam: A Traveler's Literary Companion (Traveler's Literary Companions) - John Balaban, Nguyen Qui Duc
Vietnam, 5th: Tread Your Own Path (Footprint - Travel Guides) - Claire Boobbyer