Oh, this is a tough question. Last year I was in a fairly dark place professionally and read relatively few books because I spent nearly every waking moment at work and when I was home all my thoughts were work related. It was a spell of sickness that took me to realise the inner battle that I had been having with myself for months and I finally left my last job, before it almost finished me off.
What I did read was easy reads - books that allowed me to not think or analyse the storyline, but to simply disappear into a world that was absolutely not mine. I re read a lot of old faithful books. So, I guess rather than name a title, that if a book, even a re read allowed me to escape into a book world then it achieved what I wanted it to; and turn what was a dark year into something a little brighter.