We were liars by E. Lockhart

I read Gone Girl a while back and loved it.  I knew really nothing about it and loved the suspense and intrigue of it; I couldn't put it down.
I found We were Liars on a book list titled something like "If you liked Gone Girl, you might like..."  I downloaded on my Kindle and read it a few weeks later.
Since I was expecting the suspense! intrigue!  mystery! I had high expectations of this book.
It didn't quite deliver.  I read with so much anticipation of being shocked, that it diminished the actual shock value.
Cady (Cadence) is the oldest grandchild of a wealthy New England family that summers on the same idyllic beach island that they own.  One summer, Cady wakes up on a beach with a head injury and no memory of what happened. Her besties, Gat, Mirren, and Johnny are vague and don't have contact with her for the next two years until Cady returns to the beach.  Although her injuries cannot be medically explained, Cady is left with debilitating headaches, fails out of high school, drops sports, hobbies, and essentially falls off the life grid. 
Eventually the mystery is explained.  I didn't quite see it happening, so that was a welcome surprise, but I also didn't quite buy the story.  It is a good book, worth the read and its a very quick read, I just should have read it with lesser expectations.