Space Empires V, like its predecessor, is a brilliant turn-based strategy game. Research is deep and complex. The AI, with mods, runs well. Ship design has interesting nuances and micromanagement isn't overwhelming even in the late game. Diplomacy is good enough and resource management isn't that easy but isn't overly complex, either. The modding community has created some absolute masterpieces for this game, as well.
Of course, then, there must be a caveat. SE:V is one of the buggiest games to exist in recent memory. It was designed to run with DX7.1 and DX8 on Windows XP machines. As technology marches ever onwards, getting SE:V to actually install and work even remotely properly has been a source of constant headaches. Provided you're willing to go through the slog of troubleshooting cryptic error messages, forum heresay, and troubleshooting myths from people who are taking potshots in the dark, SE:V is a game that I wholeheartedly recommend. Otherwise, stay away.