I use a star-shaped based rating system depending on how much I liked the book.
5 stars: ★★★★★
Absolutely loved it! Amazing! New favourite of mine and would highly, highly recommend to everyone! Definitely would re-read again, many, many times.
4 stars: ★★★★
Great! Not enough to be on my favourites shelf, but still great. Would still highly recommend.
3 stars: ★★★
This was okay.! Has its flaws which made it less enjoyable but still has good moments.. Would be less inclined to recommend.
2 stars: ★★
It was pretty meh. I have impartial feelings towards this book.
1 star: ★
Did not like. At all.
Please note that I also do .5 ratings as well.