As the overpopulated, multibillion-dollar fragrance industry introduces hundreds of scents every year, choosing one that smells and feels right can seem daunting. To assist in the pursuit of perfume, industry veterans Sarah McCartney, founder and perfumer at the London scent brand 4160 Tuesdays, and Samantha Scriven, who runs a blog called iscentyouaday, lend their encyclopedic knowledge of aromatic liquids to their upcoming book, The Perfume Companion: The Definitive Guide to Choosing Your Next Scent (Frances Lincoln), out next week on Kindle and in hardcover on November 9. Fluent in the science behind the olfactory system, the psychospiritual history of scents, and the deceptive power of a flashy bottle, the pair’s guidance comes across like a close friend with a highly discerning nose.