The End of Mr. Y by Scarlett Thomas

Ariel Manto has a fascination with a 19th century scientist by the name of Thomas Lumas. His rarest work, 'The End of Mr. Y', was written before his disappearance, and the same fate seems to have befallen all the book's few readers ever since. When Ariel uncovers a copy in a second-hand bookshop, she is launched into an adventure.