Below Stairs by Margaret Powell is a memoir of working in service during the interwar period. It's a short book that's witty and fun to read, especially her observations of her family, the work she did and the people she's working for. It was one of the inspirations for Downton Abbey too. Powell did write a sort of fictional book about the true romance between a maid and her son's master in a house Powell worked in, called Servants' Hall: A Real Life Upstairs, Downstairs Romance. I haven't read it yet (it's on my long, long list), but if it's anything like her memoir in style then it should be pretty good.

Life Below Stairs: in the Victorian and Edwardian Country House by Siân Evans is also non-fiction. I didn't find it dry or boring at all, but then I read a lot of academic texts so I have a high tolerance for dry and boring...