Obtain the permission of the original author to rewrite the book. An acknowledgment should be included in the edited book in the form prescribed by the copyright owner.
Review the overall style. Read the book aloud or have someone read it to you. Determine if the writing is smooth and natural. Highlight any weak areas. Note if the book was written with a clear goal in mind. Determine if the ideas expressed are concise and direct. Decide if the writing sounds authentic and honest. Make notes of what to change.
Examine sentences. Check for clarity, conciseness and variety. Make a note to replace sentences that are wordy or rambling. Combine or expand sentences that are short and choppy. Edit sentences that contain unclear wording.
Consider word choice. Be alert for words and phrases that are used together but mean the same thing, or close to the same thing. Watch for repetition. Unless the book requires it, replace highly technical terms.
Analyze the voice of the book. Notice the narration. Make a note to replace passive verbs with active verbs. Determine if the voice is predictable or fake. Replace bland expressions. Think of revising as an opportunity to energize the book.
Correct grammar is an essential component of any good writing. Grammatical errors and typos distract from the story of the book. Re-read the book with grammar in mind. Make notes and suggestions as you go along and use them when you do the revision.