This is my rating scale. This is how I rate, regardless of what any other site uses to determine a level of enjoyment:
★★★★★ -- Loved It! Definitely a keeper! Likely to be re-read! This book really grabbed/spoke to/excited me! -- I will read more from the author.
★★★★ -- Really Liked It A Lot! Great read! -- I will read more from the author.
★★★ -- Enjoyable Read. Held my interest. Felt I got my money’s worth. -- Very likely to read more by the author.
★★ -- Just OK. Finished the book. Had some enjoyable moments. Book was hard to get into and/or hold my interest. Just wasn’t to my taste. -- Depending on the reason the book didn’t appeal to me, I might try to read something else by the author. Will check out reviews first.
★ -- Finished it, but wished I hadn’t. Book may have had potential (3 or 2 star level), but failed to pay off in the end. -- Like the 2-star rating, whether or not I read the author again will be determined by the reason the book disappointed me.
DNF -- Did Not Finish. Could not make myself finish reading it. -- Again, the reasons for not finishing the book will play into whether or not I read the author again (In recent years, I haven't felt motivated enough to write one; however, there are a few that I might cross-post to Booklikes from my blog).
At this time, I have no plans to use them, even retroactively. However, starting in 2014, I'll consider using half-stars on books read from 1 January onward.