[This review is for the HarperCollins facsimile reprint edition, published in 2005]
First published in 1942, The Body in the Library is the second Miss Marple Mystery (after Murder at the Vicarage, 1930). It's very good - easy read, wry, witty, twisting plot, only takes a few hours to read - perfect for a holiday mystery, or a quick read when you want a good book, but not one that's too in-depth. I was guessing right up until the end in this Miss Marple and didn't manage to guess the right murderer at all, so hats off again to Agatha Christie.
A note on the edition: I love these HarperCollins facsimile reprint editions of the First Editions (the original Collins Crime Club editions). The dust jacket covers are so much more appealing and iconic than most of the paperback versions that came afterwards (1960s and 70s covers would often have a pool of blood, murder weapon, bottle of poison, or whatever else was relevant to the plot adorning the front cover). These covers are more suitable to the story - gentle Golden Age crime and mystery writing at its best - not gory, not graphic, just good old-fashioned honest detecting.