Does he have a mug with the caffeine symbol on it? If that's too much of a chemistry thing, maybe No flux given or this physics joke.

For reading, I'm dying to try Vellum & Bloom, which recommends a rarer, new book from a small press based on his interests. Maybe a book on electronic music?

I just got my husband this $5 tea sampler that comes with a $5-off coupon on your next order. One taste test and he's smitten with it. It's superb tea.

Also, what if you gave him the gift of time? Either time with you, or, if he's an introverted type, an afternoon to himself. Like, talk his best friend into doing his grocery-shopping for him, and pay one of those laundry-by-the-pound places to do and fold a couple loads. Have him reserve an afternoon for "special birthday stuff," then take a few things off his plate, give him his presents, and tell him to go do whatever he wants, because there's nothing else he needs to do but read/explore/make tea.