Google has a very sizable preview (maybe more than 80% of the book).
Certainly this very large preview is more than sufficient to get a feel for whether you would enjoy owning a copy.
http://books.google.com/books?id=OgiHIGOixsMC&lpg=PP1&ots=KXDwHBPKvT&dq=grimiore%20of%20the%20necronomicon&pg=PP1#v=onepage&q&f=false
Personally I found it very interesting and even a little exciting at first, but that initial flush of enthusiasm has been tempered over time.
I'd recommend getting it if you are interested in:
1) Seeing a particular magician's ideas on how to use the Mythos for magick
2) Would like to see a gnostic interpretation of Lovecraft (based mostly on exploring the parallel between the Barbello myth of Gnosticism and the "fallen earth" theme mention in the Dunwich Horror)
3)have a fondness for Tyson's apocalyptic interpretation of the Enochian materials.
Without one or more of those interests you probably wont like the book much.