How long have you been waiting for the right moment Harry? Your fear isn't getting you any closer to resolving the problem and it could very well be making it worse! Michele's point about "doing more of the same" just is not working! OK, what is the worst thing that can happen? Stop chickening out! She needs to KNOW that everything is NOT fine.
I can't remember, are you seeing a counselor? Could you tell your W that counselor wants the two of you to read the book together? It's a few weeks away, but maybe you can include it with some roses or whatever romantic stuff she likes for Valentine's Day?
If you're this fearful of asking your spouse to read a book... how can the rest of your marriage be good? If she loved you enough to marry you and have children with you, one could only hope that she could read a freakin book for you!! The initial reaction may hurt you, but it'll only be a matter of time before she opens the book and reads. Stress that it isn't an instructional how to please your husband book!
Stop stalling - just do it. Your letter is great... give it and the book to her. *please*