This question was posted in my Facebook Group "Anointed Scribes Café Christian Writers Self-Publishing Support Group." This is a question that, as a book coach, I often hear, so I decided to do a quick post for those who have the same question.
As far as the book cover it would depend on the type of book you are redoing. For instance, if it is a business book and your book cover no longer matches your business message, look, and feel, then I would say a new cover is best, so everything looks consistent and more uniform. If the information you originally shared has updated, say technology has changed, chapters have been deleted, or you are adding chapters, or you just got the rights back from a previous publisher then a new cover makes sense.
If the majority of the material is the same, and you are only correcting grammar, punctuation, etc., then a new title and book cover isn’t necessary. Also, rather than calling the new version a "second edition" you might call it a “revised edition.” A second edition would generally have the same title as the first book. Also, a new or revised edition is considered a different product and needs its own ISBN.
So, are you considering doing a second edition of your book? Why? Do you have a publishing question? Feel free to ask here as a comment and I will answer, or join my Facebook Group “Anointed Scribes Café Christian Writers Self-Publishing Support Group“ and fellowship with other kingdom Writers.