These are 2015's top books of the year so far (I eliminated rereads from consideration, which is why Lord of the Rings, among others, isn't on this list):
North and South: this was one of my first books of 2015. I had seen the mini-series (Richard Armitage, sigh), but hadn't actually read any Gaskell. I loved the fact that this book is set in the north of England during the Industrial Revolution. John Thornton is the ultimate in romantic heroes.
I'll Give You The Sun: this book was simply splendid. It was beautiful; joyful and bittersweet simultaneously. There was nothing about it I didn't love.
17 & Gone: I struggled with which Nova Ren Suma to choose for this post. The Walls Around Us was probably technically superior, but I felt like this one edged it by a hair.
The ABC Murders: I've read a lot of Christie, but this is the strongest of the new ones that I've read this year. A total blast.
Bury Your Dead: The entire Chief Inspector Gamache series is exceptional, but this was an exceptional book in an exceptional series that should be read in order. So do not start with this one.