All the information is typed directly into fields in wordpress
Since the custom fields can only be accessed when in the WordPress installation, I'm afraid you won't be able to insert them into the email.
So I feel it looks confusing to immediately start an email with "I thought this book..." (for example) without any details about the book.
You could set your RSS feed settings to "Summary", and fill the "excerpt" box for each one of your posts. There you can include a small summary of your post, and why people should click to find out more about the book and your review.