Polish puts the "book jacket" in a file called 'jacket.xhtml', immediately after the cover page ('titlepage.xhtml') - I prefer to have it at the back of the book, which is easily done with the editor - just drag it there in the file list.
Suggestion, instead of appending your review to the Comments column, where it could get overwritten by a subsequent metadata download, add a custom column.
Show it as an icon in Book List
You can edit it in the Book List by tabbing to the icon and pressing F2
You'll probably want to check the Review column in the
Look and Feel->Book Details tab, I would position it immediately before Comments.
BR