The King's Curse by Philippa Gregory, 2014
The King's Curse is about the 3rd or 4th Gregory book that I have read.  She brings the world of 15th Century royalty to life.  The power, drama & sex (especially when the story involves Henry the VIII.

The story is told from Margaret Pole's, Countess of Salisbury's, point of view.  She is a Plantagenet/York, a family feared by the Tudors.

The cousin of Henry the VII's wife, Margaret becomes the governess for future king Arthur, Prince of Wales.  With Arthur's early death from the Sweat, Arthur's younger brother Henry VIII becomes the next in line.

In and out of favor of the royal court, Margaret is thrown into poverty after the death of her husband.  With the ability to regain a place in the court for herself and her son if she betrays Princess Katherine, Author's widow, from Spain, Margaret chooses to remain faithful to her friend and former charge.

Once Katherine marries Henry VIII after his father's death, Margaret is brought back to court and bestowed lands and titles.

Unfortunately, as Henry VIII becomes more paranoid and obsessed with fathering a male heir, those close to him are mercilessly sent to the Tower and charged with treason for the barest offense.

The Hopefuls by Jennifer Close, 2016
Captures DC perfectly.  Captures marriage and couple-friendships perfectly. 
Midwestern Beth is married to Matt, whose family fashions themselves after the Kennedies. 
Matt grew up knowing he wanted to run for office and purposefully abstained from any questionable behavior while growing up to prevent any embarrassment when he ran for office.  A friend's husband that I knew in DC behaved the same way.
New to DC, Beth and Matt befriend Texans Ashleigh & Jimmy. 
Despite having a very "DC" relationship, Beth appreciates Ashleigh & Jimmy because they are the rare political couple who can talk about other things besides politics.
When Matt signs on to run Jimmy's campaign, the stress of the campaign, especially a failing one, becomes too much for everyone involved.