Whether or not you enjoyed Fifty Shades of Grey, you will enjoy this if you are familiar with the famous work by Jane Austen's Pride and Prejudice. I would say you have to be familiar with both works to fully appreciate the quotes William Codpiece Thwackery adapts and the ingenious way in which he/she merges these two story lines together. I believe you do need to have read Fifty Shades for simply knowing the story line is not enough to pick up on the ridiculousness Twackery is satirising.
But as soon as you get passed the shocking bastardisation of this beloved Regency novel where decorum and reputation mean everything, the story grows tired and become decreasingly entertaining. Christian Grey certainly has some characteristics in common with Fitzwilliam Darcy which makes Twackery's Darcy very... ridiculous.
The narrative occasionally breaks the "fourth wall" and acknowledges that some details belong to neither story. The first time the characters realised this and point out they should just move on, it is funny, however, the fourth or fifth time is too much. Also, the author deliberately uses anachronisms to increase the parodying trend of the book.
The title, Fifty Shades of Mr. Darcy, makes it very clear what is to come and given that Fifty Shades was not a great book to begin with -- it was after all started as a fan fiction of Twilight of all books! -- this book really is "tolerable I suppose, but not [clever/witty/high-brow/original/etc./etc.] enough to tempt me." After the first fifty pages or so, I was over it.