There's three categories of books I can't read while I'm writing. (Writing meaning first-drafting; chipping the virgin story out of the ground.)
1. Books similar to mine that I want to be able to say I didn't read and haven't stolen from even if we've both got retired burlesque dancers who fly the first air ambulances in Worcestershire and killed their twin brothers with a grapefruit spoon.
So that's Jacqueline Winspear and Rhys Bowen - the other two blonde Brits who live in northen California and write amateur detective stories set in the UK in the 1920s. And Carola Dunn (as above except it's Oregon) and Kerry Greenwood too. Which is a lot of great books to not read. Moof.
2. Books in the wider genre so breathtakingly, heartbreakingly fantabulous that I'd get a case of the why-bothers only Ben, Jerry and Sheldon Cooper could cure. This sees off Dennis Lehane, Ruth Rendell and Ann Cleeves. There are more but I need to stop now because even listing them is dispiriting.
3. Books by writers whose style is insidiously contagious (and who are too famous to hyperlink).
Raymond Chandler is just about the worst of these. I was reading him once while writing and decided that Dandy Gilver's tea frock could fit her like a mermaid's scales. Why not? (I caught it in the edit.)
Ernest Heningway isn't worth the risk either. Nick and the fish and the big two-hearted river? Hugh Gilver sometimes poddles off with his rods hoping to catch a salmon but it's not the same.
But pipping them both at the post (or poking them both smartly in the second waistcoat button, as he would say) is PG Wodehouse. Some of Wodehouse's lines make me laugh out loud no matter how many times I've heard them. When Bertie Wooster had a hangover and "a cat stamped into the room". Or when Mr Beach is displeased but says nothing and PW describes it thus - "ice formed on the butler's upper slopes". Genius. Or when . . . I think it's Bingo Little . . . sends a telegram that begins - "I say Bertie old boy stop yes Bertie stop I wonder old chap if I might have a word stop" The narrative goes on - "The telegram is not Bingo's natural form."
So part of the joy of getting that first draft done is to be able to read absolutely anything again. Mystic River or Right Ho, Jeeves. The world's my TBR pile.