Nothing Ever Happens Here, by Sarah Hagger-Holt

Nothing ever happens in Izzy's quiet little town.  But all of that is about to change when her father announces to the family that he's actually a woman and has decided to come out as Danielle.  Izzy's little brother is too young to understand and wonders if it is a secret superhero thing.  Izzy's older sister is outraged about what this will do to her standing at school.  But Izzy herself worries that this means that her Dad is no longer going to be her father.  Through many supportive conversations with friends and each other, Izzy's family learns how to adapt to the change, rethinking their own family unit and dealing with the reaction of their neighbors and friends.

Geared towards a younger YA audience, the story does a good job of covering a wide variety of topics ranging from practical questions like how the kids will address their father to how they deal with a broad range of emotions (confusion, anger, grief, joy, etc.) that each of the family members experience. What truly makes the book shine is that it never gets preachy or teachy, but manages nonetheless to bring up a plethora of important issues while doing so in an entertaining way.

Like many British YA novels, the book assumes a level of innocence that you wouldn't find in an American treatment of this topic, but that actually serves the story well in this case as the adults are actively supportive and responsible.  As difficult as the changes may be for all, no one expects the children to deal with matters on their own.