Evaluate the book's basic information before reading it. What is the genre? This will affect what events are and are not credible in the story, as events that are acceptable in a horror novel would be out of place in a Western. Is the book written for children or adults? If the book is nonfiction, is it written for laypeople or for experts in the field?
Research the book to build context. Read a short biography of the author or visit his website for more information, and read as many of his other books as possible (although you may have to read summaries to save time). If the book is fiction, read other novels in that genre so you are familiar with its tropes and cliches. If the book is nonfiction, read other books on the same topic so you know how much of the information is feasible, how many of the ideas are original and whether any crucial details are left out or trivial details are overemphasized.
Jot down any expectations you have for the book based on its book jacket description or the author's previous work. Because this is specifically a first-person book review, you may want to personalize it by describing your own changing relationship with the book. You can do this with sentences like "I was skeptical of X's claim at first, but when I began to read his book, I found myself increasingly convinced," or "I expect romance with a hint of melodrama from Y, and this book did not disappoint me."
Take notes as you read. For fiction, make notes on whether the characters are believable and sympathetic and the plot is logical. For nonfiction, look for accuracy, use of sources and an authorial voice that makes the subject matter interesting. Regardless of whether you are reviewing fiction or nonfiction, look for the book's theme or thesis. Note whether the author consistently supports it or seems to undercut it and whether her treatment of it is too heavy-handed or strident. You might also evaluate the worthiness of the theme or thesis itself, as some authors use their books to advance weakly supported or morally problematic ideas.
Organize your notes into an outline once you've finished the book. Begin with a brief summary of the book's premise, being careful not to give away the ending or any major plot twists. Continue into an analysis of what you consider to be the book's greatest strengths and weaknesses. The most logical way to arrange this is to begin with either the strengths or the weaknesses and then move on to the other. Include notes on how you felt when you read these good or poor parts of the book.
Write your review based on your outline. When writing your review, use personal statements using first-person pronouns. Rather than saying, "The protagonist behaved in an unrealistic way," say, "No matter how hard I tried, I could never make myself believe that the protagonist was a real person." Include specific examples from the book to back up your statements, but do not use any that give away major plot twists.