My brother and I enjoy games like Magic, Star Realms, Android: Netrunner, etc.
However, I know that he would prefer to have a game with this level of strategy and variety-of-card, but that is an abstract game, like regular playing cards, chess, etc. so that he can play it in public without feeling like a nerd.
Does such a thing exist?
I can’t think of anything off the top of my head that approaches that level using a regular deck of cards.
www.pagat.com claims to be the largest repository of card game rules on the internet.
He could just play solitaire with a Tarot deck and freak all the newage astrology types right the fuck out.
Fizzbin?
All I can think of is a Rummy variant called 5000.
How “abstract” would you consider Fluxx? It does require its own special deck (i.e. not an ordinary deck of playing cards, but all Fluxx decks are the same - that is, all “base version” Fluxx decks are the same; there’s also Eco Fluxx, Monster Fluxx, Star Fluxx, Monty Python Fluxx, Zombie Fluxx, Stoner Fluxx,…
The concept is simple - each player turn prety much consists of drawing cards (“How many?” Well, at the start, one, but there are cards that can change this) and then playing cards (“How many?” Well, at the start, one, but there are cards that can change this) until somebody meets the current “goal” condition and wins (“What is the Goal Condition?” Well, at the start, there isn’t one, but there are cards that can change this…)
How about Decktet games? Decktet is a deck of cards with suits and rankings, like one expects of a deck of cards, but cards can have multiple suits and the distribution is not consistent with a normal deck of playing cards. They sell a book of Decklet games and the cards on the website. There are a couple of Decklet games available on Android if you want the flavor, Adaman and Goblin Market.
This was gonna be one of my recommendations; it’s great fun and very easy to learn.
I can also recommend Munchkin. It’s a card game that has you exploring a dungeon. Tons of fun and lots of replay value.
If you want a game that uses cards but isn’t really a card game, you can’t go wrong with Illuminati. It doesn’t get any more convoluted than this game, believe me. 
And an old favorite of mine, Nuclear War and it’s expansions are still published by the venerable Flying Buffalo, Inc.
It doesn’t need to be a regular deck of cards, it just would need to be a deck with no fantasy/sci-fi art on it.
Something like “We didn’t play test this game” would be fine, because it’s just text on cards. Of course, that’s just random funny things rather than a strategy game.
Oh, then yeah. Lots of choices.
That one is pretty good, and works nicely with two players.
Another good one by the same designer, provided you can get your hands on it, is Glory to Rome. The art from the Black Box Edition will bring whatever the opposite of “feeling like a nerd” is.
Based on a youtube review, this one looks like the manual and setup are pretty involved. I think that might throw your average non-nerd off.
Innovation might be okay. There’s still some art on the cards, but it looks reasonably perfunctory.
Mao is pretty abstract and convoluted and is played with a normal deck of cards.
I really like both Glory to Rome and Innovation. Innovation is available for free online with the creator’s permission at http://innovation.isotropic.org/ if you want a taste.
Setup for GtR isn’t that complex, but the way cards are used is … not intuitive. It takes some learning, but it’s well worth it. Most people have it figured out by the end of the first game.
Be warned that both games are deeply strategic but not balanced in the way most deep strategy games are. They’re broken, but in a good way. There are cards in Innovation that are so fundamentally weak compared to other cards of the same age that they are virtually never played deliberately (for their abilities - they might be used for icons). In both games, the fun in both is trying to break things better than your opponent.
I don’t know if it still exists but I used to play a game called Illuminati. It was a fun, silly game that was kind of like a CCG but you got all the cards in the box.
Each player was a different secret society and one of the fun aspects is each player had a different win condition.
It still exists; in fact, Steve Jackson Games still sells it.
Actually, there are two different versions: “normal” Illuminati, where you get all of the cards in the game at once, and “Illuminati New World Order” (or “OMNI”, which is how the logo appears if you hold the box upside-down), which is more of a CCG, although the “One With Everything” set has one of every card. As far as I can tell, only the first version is still available.
Glad to hear it’s still around. It was fun. Another game I played back then was also with cards called Family Business. It was a Mob war game. Nowhere near as complicated as Illuminati but fun.
how about mobile card games on your phone or tablet? they could be relatively private.
If the goal is to find deep card games with less-themed art, then my opinion would be that the complexity of the manual/setup shouldn’t matter that much. FYI, the complexity is comparable to the other games you have mentioned.
If you’re spending half the game thumbing through a 20 page manual, I think people will figure out that the game is expected for people who are more involved in their gaming than is seen as respectable.