A collection of 16 stories by the master of classic horror/science fiction/weird fiction. If you're not familiar with Lovecraft's work, well, shame on you (though I confess my own belated discovery of his genius occurred in the not-too-distant past, so I won't judge you too harshly).
Why should you know and love Lovecraft? For starters, a lot of really cool people like him--he has influenced a number of writers, including Neil Gaiman (American Gods), Alan Moore (Watchmen), Robert Bloch (Psycho), Robert E. Howard (Conan the Barbarian), and Stephen King (everything), as well as directors Guillermo Del Toro (Pan's Labyrinth) and Sam Raimi (Evil Dead) and a variety of metal bands. Also, the man has left an indelible mark on popular culture, and you'll find yourself catching Lovecraft references in Army of Darkness, Babylon 5, The Real Ghostbusters, Night Gallery, and pretty much every Batman movie ever, just to name a few. You need to know this man's work.
Fortunately, this collection is an excellent means of remedying your tragic under-exposure to to Lovecraft's eerie prose.
This is not your modern day slasher horror--there is more suggestion than gore, more anticipation than attack. The antiquarian language (great for boosting your vocabulary) merely adds to Lovecraft's charm. I particularly enjoy his delightful habit of somehow both under- and over-describing the creative and unsettling horrors his characters experience. Never have so many adjectives been used to say so little. Lovecraft is the master of evocative language, and he somehow conjures up all sorts of terrifying and otherworldly monstrosities without actually describing anything--which makes him a favorite of imaginative readers everywhere.
The stories, ranging from 6 to 60 pages in length, can easily be read in a single setting, making this a great commuter book. My favorites in this collection include "The Whisperer in Darkness", "The Colour Out of Space" (though American, Lovecraft was a total Anglophile, hence his persistent penchant for British spelling), "The Thing on the Doorstep", "The Shadow Over Innsmouth", and "The Call of Cthulhu."
Bonus recommendation: The hilarious and insightful podcasts over at The H.P. Lovecraft Literary Podcast are a great supplement to Lovecraft's work, and point out themes and ideas I never would have noticed on my own.