With the burgeoning popularity of the Cthulhu mythos, HPL et al's work and creations have gained a wider toehold with the general public. Many people have heard of Cthulhu without ever having read Lovecraft's original The Call of Cthulhu. There are rpg fans that play the Chaosium game or the Fantasy Flight collectable card game without reading the original source material. Hence there is a demand for a sort of Cliff notes for the Cthulhu mythos. I know of several such books in the last few years.
The Lovecraft Necronomicon Primer: A Guide to the Cthulhu Mythos by T. Allan Bilstad from LLewelyn Publications came out in 2009, and it is a similar reasonably priced introduction to the creatures and stories, leavened with humor.
Much shorter and more humorous (and a few dollars less) is Cthulhu 101 by Kenneth Hite from Atomic Overmind Press, also published in 2009.
For the more serious aficianado, Mr. Hite wrote Tour de Lovcecraft: The Tales, a 2008 offering from Atomic Overmind Press. This is a companion, an opinionated annotation to the best of Lovecraft's stories. It is not meant as a substitute for reading the actual stories!
To best put HPL into context, more serious students will read ST Joshi's The Rise and Fall of the Cthulhu Mythos from Mythos Books in 2008. This is also a very opinionated work but offers invaluable insights regarding the evolution of HPL's place in popular culture from the most highly regarded Lovecraft scholar of the modern era.
The mythos critter geek will be happy as a shoggoth in mud with Daniel Harm's The Cthulhu Mythos Encyclopedia, 3rd edition from Elder Signs Press in 2008.
RPG freaks prefer the Malleus Monstrorum, edited by Scott David Aniolowski and reprinted in 2006 by Chaosium, and the two hard to come by field guides by Sandy Petersen.
I have all of these books but only a a complete mythos idjit needs to go to that extreme. Which brings us back to the current book by Rachel Gray. I have never encountered her name before; I gather she has worked behind the scenes in several companies that produce mythos works. She wrote this with heavy encouragement from ESP maven William Jones. With the low list price, and the discount and free shipping from Amazon, you have practically nothing to lose for a handsome 256 page book. The writng style is breezy, there is a lot of tongue in cheek humor and there is also a reasonably comprehensive look at HPL's most famous work. My biggest problem is the same issue I have with any such book. I don't really see the need for a synopsis. Why not read the originals. The text of all of HPL's big works are available online for free or at the local library if you are too parsimonious to buy a collection. His prose is very 1920s and long winded but you miss out on the reason for HPL's pervasive influence on 21st century horror and science fiction if you just skim a book like this. If you are already familiar with the work of HPL and the various Lovecraft circles, then the reason to sample What to Do When You Meet Cthulhu is for the humor. Maybe I should stop sampling these guides, because I find the humor becomes stale after only a few pages.
Most fans who get a copy of this book will be happy with it, I suppose, and it is a bit of a bargain. It is an undemanding very quick read that can occupy you for a night or two. The reason I recommend this more highly than The Lovecraft Necronomicon Primer is the excellent cover by Steven Gilberts, and attractive interior art, also partly by Mr. Gilberts. Not a replacement for reading Lovecraft What to Do When You meet Cthulhu can be a pleasant diversion for idle tentacles.