I write contemporary romantic fiction and I love reading it. When the book is excellent, it's quite depressing, but when it's not so excellent, it will boost my self-confidence.
I like thrillers and mysteries too, but I find it helps to read in the same genre as I'm writing to get in the mood. I noticed that my sentences became blunter and shorter when I was reading thrillers so my pace speeded up when the scene didn't require it.
I know lots of experienced writers prefer to read in another genre to avoid being influenced by what they're reading. They're naturally worried that the contents might implant surreptitiously in their mind and they'll accidentally pour it out on their manuscript. This worries me of course, but I think this could happen with any genre you read or even watch. An idea, character or scene might sneak in from a murder mystery too and transform somehow into a love scene in your work in progress.
Maybe I'm relying too much on my memory, and I think I will remember what I've read. But I can't imagine not reading in the genre I love and I've got so much to learn from the people that master this genre, I feel it will only help me improve. However, I will go to extremes if I think something might have any similarities with what I've read and sometimes there is not really any resemblance at all, only something that triggered a memory of that book, even something meaningless, like the colour of a wall.
What do you read when you're writing?