A five star book is one that I recommend very highly and surpasses all my expectations. It needs to cover fresh ground, and offer something amazing to the reader. It needs to stick with me when I am done reading it and be one with no discernable flaws. I do not often give this rating. Sometimes it is so wonderful that I have trouble putting into words exactly what made it worthy, but that is on me rather than the book.
A four star book is one that I really enjoyed and feel that is a wonderful example of its genre, or offers characters or plot twists that really captured my interest. There might be a flaw or two, but nothing that makes the book less enjoyable. Sometimes something will not work for me, but I can recognize that other readers would consider this book a five star read. It is a book that I would definitely recommend to other readers.
A one star book is rare here. For me to actually finish a book that left me cold enough to leave a one star review is unusual. These are not just books that leave me feeling uncaring about the book, but actively unhappy that I finished the read. If a book is rated as one star it is only because I want to actively discourage others from reading the material- which is not normally my style. I can usually see something good in everything, or think of a certain group of people that would enjoy it. These books are ones that left me with little or nothing nice to say.