Why does this seem not-at-all familiar?

It's happened, you guys. I borrowed a book from the library that I've already read ... from the library. I honestly feel like there needs to be some kind of online buzzer or bright red, capped notification when you request a book that you've already borrowed once before. And it should be vaguely insulting too. Like, "Kimberly? Are you sure you want to borrow this one? Maybe reread the synopsis and be sure it doesn't seem a little familiar? *heavy sigh* You read this last year, dork."
What concerns me is that I did read the synopsis, in Barnes & Noble. Yes, I actually held the book in  my hands and thought, "This sounds good. I should read it." Not for a second did it seem familiar. Not. For. A. Second.
I mean, I know I read fast, and I certainly know that my casual, pleasure reading ranks incredibly low in my comprehension skills. The books are like fun, wispy clouds that float in and around my head for a bit before fading away. Books and stories I remember are books and stories I have re-read a couple/few times, or which qualify for life- and conscience-altering status. [Editorial note that I still can't spell "conscience" correctly. Twice I needed auto-correct in two consecutive sentences.]
But here's the real weird part. This particular book is the first in a series of three. That means that I read THREE books about those characters, but still didn't remember them enough to have any bells go off in my head while reading the book flaps. Jeez.
So, needless to say, this really doesn't stop me from simply shrugging my shoulders at my bad memory, returning this book, and picking up something new this afternoon. I LOVE READING!