I am getting on well with writing the first book in an intended novel series based on the mystery/crime format. I have taken the characters from an (unpublished) novel I completed in 2005 - which I had a go at re-writing in 2011 - and given them another good shake.
I am following Minette Walter's advice in creating a mystery: start with the characters and a scenario without knowing 'who dunnit' and allow the solution to reveal itself. Surprisingly it is working so far.
I am also finding the truth in something else novelists often say, that characters take over and write themselves. I have one who at the beginning was pretty minor, who is now muscling in on all the action. It's a very interesting process.