New depths of regifting

My son has a bookshelf packed with books. He doesn't browse his shelves the way I always did (and still do) and he doesn't have as merciless a grip on what he owns, bookwise, as his book-mommy does. I've been known to sneak a book off his shelf while he's asleep and wrap it up as a "new" gift for him. What's sad is that his dad is utterly unconscious that any ruse has occurred, and congratulates me on making a fine choice of gifts. Admittedly, we do a lot of little-gift giving on holidays most other people don't even notice. I’ve only done this on minor occasions, not on Christmas or a birthday. But I'm sure that's next.