I just finished "The Invisible Bridge" which was an amazing story but not really a light summer read... though I read it at the pool.
I do recommend it though.
Currently reading "Elizabeth the Queen" by Sally Bedell Smith... if you are interested in what her life is really like (it's not titillating though I didn't realize that her sister and other relatives had such troubled personal lives!) then I recommend it. She is a hard-working lady!
Another series (light, easy read) I have recently enjoyed is "Her Royal Spyness" by Rhys Bowen... another series set in the same time (post WW I Britain) is the Maisie Dobbs series by Jacqueline Winspear.