My main campaign puts a lot of emphasis on good storytelling and fun gameplay, as opposed to for example a more harsh rule-bound game.
Same. I enjoy both styles but can satiate my sporadic rules-heavy cravings by launching one of the harder roguelikes.
It's not just a practical gift
I get that. And in case I said or implied something to the contrary: it is a great, thoughtful gift.
Though, speaking from experience, DM Manual is principally useful for D&D whereas books like Trap Compendium can be easily refitted for most other games, not exclusively the fantasy/high magic ones. If you are unlikely to change the system anytime soon, then it's a moot point. Otherwise… that's part of what I meant by the 'gift that keeps on giving' remark.
Either way, all in the name of fun.