SHOGUN 2 is both a turn based strategy game and a real time strategy game. It is bursting with atmosphere with the time, and you'll find yourself wanting to watch old Kurosawa films and drink sake more and more.
The dephth of tactics and diplomacy can be startling, but near the end though it does railroad everyone against you (Realm Divide). Something I don't like, but makes it more of a challange.
Co-op campaign mode is one of the best experiences I've had in gaming (although it is sometimes buggy, leading to crashes and corrupt game saves). Strategizing grand campaigns and economic warfare agains other clans with a friend is very satisfying, and having them use some of your troops during your battles keeps everyone entertained and engaged.
I recommend it RTS fans, and I think they'll have a lot of fun. The battles can be quick paced, and the gameplay between them both relaxing and entertaining.