The Paying Guests by Sarah Waters

Francis and her mother find themselves is desperate financial straits following WWI and are forced to rent out the 2nd floor of their London home to "paying guests" - a term designed to keep them from having to admit they are taking in borders.  Leo and Lily, the renters, seem to be an interesting young couple.  Assuredly they are of a lower class but Francis still feels a strong attraction to Lily.  As the two women explore their strong sexual attraction, with almost no detail left to the readers imagination, lies and deceptions pile one on top of another.  Ultimately a line is crossed that puts both women in jeopardy.  This was on the Bookbub's "10 best books of 2014" list.