I am not sure I can top Katrina Lumsden's review of this book on Goodreads, but I have to say that although I cringed at the poor writing style (repetitive, cliched and uninspiring), I was definitely intrigued by the characterisation which kept me reading.
It is fairly unbelievable that a protagonist as seemingly beautiful as Anastasia Steele would have had NO sexual partners or even been interested in any by the age of 21. However, I can see how her 'innocence' is a necessary foil for the 'corrupted' Christian Grey. E.L. James uses the classic Mills and Boon 'bodice ripping' technique in describing Christian who is handsome, brooding, rich and forceful; seducing his 'innocent' victim and yet always remaining a small step out of reach. It is a formula that has kept female readers spellbound for years.
James takes this formula a stage further by incorporating the concept of erotic and bdsm literature into mainstream fiction (which from now on may no longer have its own little niche shelf in the bookshop). However, despite the initial promise of the 'playroom' and all its 'kinky fuckery', the sex is actually fairly tame, repetitive and mainly 'vanilla' up until Christian's shock leather belt beating of Anastasia at the end where she rather unbelievably forgets to use the 'safe word'.
I can see why this book is popular. Put simply, sex sells, and kinky sex sells better. It does have a bit more to offer than that but I also think it could have been much better than it actually is - think D.H. Lawrence standard who was doing the same sort of thing in his era a long time ago and with much more skill.
It didn't put me off reading the sequel though!