I think buying any book your boyfriend / girlfriend / husband / wife / mistress / mister(?) / favorite prostitute (male or female) would enjoy is a great idea for Valentine's Day, though there are a few books that are specific to the holiday. as I've said before, buying someone a book is a great way to show them you care and know something about them without having to make something yourself or go totally broke.
So, while I humbly submit that books are The One True Gift this coming weekend, I'd be remiss if I didn't ask you, dear readers, what you plan to be up to. Me? I'm going to eat my weight in Necco candy hearts and re-read Cat's Cradle.