I wrote a mystery novel. It was cumbersome and convoluted. Thought about it for a long time (a year). Used a wandering solitary road trip to get over extreme writer's block. Boiled it down to essentials. Started writing again. Ruby and all the rest were there waiting for me.
One thing I did that was helpful was to take my manuscript and just read it like it was a book I picked up, nothing to do with me. That was very helpful. I saw the faults in an objective way. I also saw the really good things -- the writing, the pace, the characters, the dialogue -- I wanted to keep reading.
I only took one book with me. I have a shelf of writing books that have come with me on this journey but I needed something practical. You can have great writing, characters, dialogue etc. but if you don't know how to plot a mystery it's all for naught. Now to keep at it.