A+ : Goes on my favorite book list. This book touched me in some way. Either I really connected with the characters, or the plot was freakin' awesome. If you're ever in a reading slump, try this one!
A : I loved this book. Well-written, good character development, fast-paced plot (or so beautifully written that I didn't care if it moved slow). Highly recommended. This is one I would probably re-read, and I will check out all of the authors other books as well.
B : I liked this book. There may have been a few things I didn't like, but the good outweighed the bad. If you're ever browsing in a book store, this might be one to buy. I will read more by this author/continue with the series (if it is one).
C : This book was okay. There were things I liked, and things I didn't. This would be a good one to check out from the library. Depending on what I liked (or didn't like), I might recommend it or read more by the author.
D : Didn't like it. Something made me finish this book, but there wasn't much good in it, and I probably wouldn't recommend it. I'd say only read this book if you have nothing else to read.
F : Couldn't finish. Either it was boring, not believable, or some other third thing. Only read this book if you're trapped on a deserted island and it's the only thing available. And even then, it might be time to find a new hobby.
Most of my reviews will be a C grade or higher. I rarely give books a D grade, because if I don't like it, I'm usually fairly quick to give up on it. There are way too many books out there to read the ones I'm not into.