I am sure that most people who receive informal correspondence such as memos and e-mail already know that the magical spell checker is not the final word in many cases.
I often get messages which contain the words "here", "affect", "principle" and others which could have passed the spell checker test, but are really wrong in the context intended. In those cases, the writer actually meant hear, effect, principal etc.
There are sometimes "rules" to help the writer remember which words to use. Like the "I before E" rule, however, these are not rules at all but lines to memorize to help spur the memory of what to use. In most cases, the only way to get the correct word is to simply memorize the words that confuse you.
This book is a great help to have at hand for those words which you did not memorize. It is a good gift book also. I have had a copy of this book sitting on my desk where I compose messages. This new copy was one that I purchased to give as a gift to my nephew who is just entering college and probably will be writing term papers, reviews or reports in the near future.