No. 42 was The Peanut Butter Murders by Corinne Holt Sawyer.
The book is the same series as No. 41 and another being weeded from the THS library stacks. It's a simple story, but the mystery held until the end. The main characters, a couple ladies who live in a retirement community, are quirky and always sticking their noses in the middle of things. A fun story.