Rating System

I have changed how I rate books so that instead of my simple 1 to 5 star rating system, I have 5 categories and an overall percentage at the end.

Plot: /10
If there was one, then great! If not, bad. I comment on whether the plot was interesting, etc.
Writing Quality: /10
How well the author wrote.
Originality: /10
If the actual story was different to others written in that genre.
Characters: /10
How well the characters were developed. Comment on personality, likeness, realisticness etc.
Descriptions: /10
How well I could imagine the book due to the descriptions in the writing.
Other comments:
Anything else to comment on outside those above criteria.
/50 = ?? %
Add up the marks, and get the overall percentage!

My older reviews will not receive this new system, so therefore, I will place the descriptions for the old system here, for reference.