It's all paws on deck as a librarian and her rescue cat track down a killer in the newest book in the national bestselling Bookmobile Cat mystery series.   Minnie Hamilton and her rescue cat, Eddie, cruise around lovely Chilson, Michigan delivering happiness and good reads in their bookmobile. But the feisty librarian is worried that the bookmobile's future could be uncertain when a new library board chair arrives and doesn't seem too friendly to her pet project.    Still, she has to put her personal worries aside when she and Eddie are out on their regular route and one of their favorite customers doesn't turn up to collect her books. Minnie, at Eddie's prodding, checks on the woman and finds her lying dead in her snow-covered driveway. Now it's up to Minnie and her friends--feline and otherwise--to find the perpetrator and give them their due.