Instructions for American Servicemen in Britain was published in 1942 and I am told a copy was given to every American serviceman who arrived in Britain. (I obtained a 1994 reprint.)
"…The British don't know how to make a good cup of coffee. You don't know how to make a good cup of tea. It's an even swap…"
"…When you see a girl in khaki or air-force blue with a bit of ribbon on her tunic, remember she didn't get it for knitting more socks than anyone else in Ipswich…"
"…It is always impolite to criticize your hosts; it is militarily stupid to criticize your allies."
"instead of railroads, automobiles, and radios, the British will talk about railways, motor-cars, and wireless"
If you would like a copy of the book your ancestor may have read, I have found it online as an ebook at http://www.hardscrabblefarm.com/ww2/britain.htm as well as in numerous other places on the Internet. You can even purchase a hard copy of it if you start your Internet search at http://goo.gl/XnYiZ.