The Murder Of Roger Ackroyd
Upon the completion of And Then There Were None, I was a mere 20 minutes into my walk and eager for more, so I fired up the old Libby app, tried to borrow this book, failed, fired up Hoopla, borrowed this book, and spent the next 5 hours in literary satisfaction (also finished the walk, mowed the lawn, did the dishes, played fetch with the dog, and lay in the hammock - a successful morning by every account).
A good, neat little small-town murder to be solved by Poirot and his moustaches. I, unfortunately, did not solve it in time, I was terribly far from the mark after a most satisfying ending.