It's not QUITE a "base builder" strategy (more of a tactical) but if you don't have it in your collection yet, X-com+Enemy Within (the expansion is the same game with more options like how the Civ games work - if you get both, skip the standard game) are almost certainly going to entertain. It's by Firaxis as well (same as Civ).
If you want a game you can play on a tablet to take on the train/plane/etc too, enemy within is available on iOS and Android (for about £7/$10) and is as good as the console versions (best mobile port ever, by an enormous margin).