This is a 1943 reproduction of the United States Army Technical Manual TM 30-302 French, also known as the "French Familiarization Manual". This technical manual was designed to help American soldiers communicate and interact with the French during World War II. 

The manual contains detailed instructions and glossaries on the French language, culture and customs. For example, it provides information on proper forms of address, politeness and etiquette. It also provides practical phrases and vocabulary for common situations, such as ordering food, asking for directions or negotiating. 

In addition, the manual contains background information on French history, geography and society. This was intended to help American soldiers better understand and respect the local population during their mission in France. 

The publication of this comprehensive manual demonstrates the importance the American military leadership felt for its troops to be well prepared and informed about France before they deployed there. It reflects the concern for a successful military campaign, but also the desire to ensure the best possible relationship with the French. 

This is a must have as a re-enactor or collector, this was part of your gear. 
Note this is of course a reproduction, originals are not really available anymore and when you would find them it is almost affordable.