From the SF/F books I read in 2015:
The Farseer Trilogy, by Robin Hobb
The Broken Empire Trilogy, by Mark Lawrence
Harry Potter collection, by J.K. Rowling
Star Wars: Darth Bane Trilogy, by Drew Karpyshyn
Nation, by Terry Pratchett
City of Burning Shadows, by Barbara J. Webb
Farseer has a great emotional aspect and characterization. Jorg and the setting are so unique and likeable. One of the best protagonists ever.
Harry Potter, because I believed they were just children's books. I was such a muggle. And Darth Bane because I never thought Star Wars would do well in a book. I couldn't even begin the original by Lucas.
Nation because it was my introduction to Terry Pratchett. CoBS surprised me by its unusual mixture as well and made me want to read the others SPBO.
I believe The Martian will end up in this list as well.
The Hunger Games Trilogy, by Suzane Collins
The Left Hand of God Trilogy, by Paul Hoffman
The Deed of Paksenarrion Trilogy, by Elizabeth Moon
I will dispense commentaries on HG. Left Hand had a great premise, but it didn't worked for me. Paks had also great premise, bogged down with too much dragging and a bizarre, surreal ending.
Had Both Highlights and Disappointments:
The Night Angel Trilogy, by Brent Weeks - Greatly enjoyed the first two books, disliked the last and hated the Durzo novella.
Agatha Christie - Four great books and two bad ones.
Perdido Street Station, by China Miélville - Loved the life of the city and its society, didn't liked when this and characterization disappeared and were replaced by the monster hunting action in the other half of the book.
American Gods, by Neil Gaiman - Excellent symbolism, hidden meanings and such, but it didn't made it any easier or enjoyable to read.