Love Nina: A Nanny Write Homes by Nina Stibbe
"In 1982, 20-year-old Nina Stibbe moved to London to work as a nanny to two opinionated and lively young boys. In frequent letters home to her sister, Nina described her trials and triumphs: there's a cat nobody likes, suppertime visits from a famous local playwright, a mysteriously unpaid milk bill, and repeated misadventures parking the family car. Dinner table discussions cover the gamut, from the greats of English literature, to swearing in German, to sexually transmitted diseases. There's no end to what Nina can learn from these boys (rude words) and their broad-minded mother (the who's who of literary London)."
This was recommended by sources that I've used before but I didn't like it. In the first place it is set in the early 80's so it is dated. Secondly it is set in England and thus the slang and popular references are completely foreign to an American reader.