The Book of the Week is Frankenstein by Mary Shelley.
In 1816, young Mary Wollstonecraft Godwin was vacationing in Switzerland with her husband-to-be, celebrated poet Percy Bysshe Shelley. (They weren't able to marry officially until later that year, when Shelley's first wife committed suicide, but there's no need to discuss all those sordid details.) They were passing an evening reading ghost stories out loud with a group of friends including another very famous poet, Lord Byron (who had recently impregnated Mary's stepsister and had an incestuous affair with his own half-sister, but we're just not going to go into all that), when Byron challenged the group to write their own suspense stories. Who could possibly have imagined that the contest would be won hands down by Shelley's teenaged bride, who would write the two renowned authors under the table and create arguably the most influential novel in the history of two different genres? Frankenstein reshaped the horror genre, and is widely regarded as the first modern science fiction novel. The novel was revolutionary in that it attributed all the strange events in the story to scientific principles rather than supernatural forces, and its theme of how technological advances may reshape human destiny - as reflected in the book's subtitle The Modern Prometheus - to this day remains the central motif of science fiction.
The true first edition of Frankenstein, published anonymously in 1818, is unobtainable for we collectors of modest means. My copy is the first paperback edition, printed by now-defunct publisher Lion Books in 1953. Note that even though this book was published well after the famous 1931 film version of Frankenstein, the cover ignores Boris Karloff's rendition of the monster and instead depicts him as the anguished person described in the book. (Compare the scan of the 1967 Bantam edition.)
Incidentally, book collectors as a group are notorious liars. Collectors call the Lion Books Frankenstein the first paperback edition, but this is blatantly false. It was preceded seven years earlier by a printing in the peculiarly formatted Armed Services Edition series of paperbacks. Next week's Book of the Week will be an Armed Services Edition book.