For August our book will be Carmilla by Sheridan Le Fanu.
Carmilla is an early gothic vampire story, predating Dracula by about 25 years. Although never quite as popular as Dracula, Carmilla is nevertheless both fun and fascinating. It’s often printed, so it should not be difficult to get ahold of, and the text is in the public domain so I will link to a free e-book version here before the book club begins.
Carmilla is also quite short—much shorter than Dracula—and is really best classified as a novella. You will likely be able to read the entire book in a sitting.