What's more embarassing than buying a book called "How to Start a Conversation and Make Friends" on a Friday night?
...Having a cashier who reads the title of the book out loud for all to hear and laughs about it. (after you carefully hid the book under your arm while browsing so no one would see)
At such a moment you may be tempted to tell the clerk that the book is actually for your mom, which it isn't, so don't. All that does is prove that you really do need such a manual.