What books are similar to Mass Effect?

In case you do not know Mass Effect is a game series but also had 4 books to go along with the games. I read the books and played the games and loved both. The books though have really given me a interest in reading more similar style scifi books. Does anyone know any books that would be similar to Mass Effect?

The Old Man's War series has similar battles.

Starship Troopers is military Sci Fi.

All you need is Kill

A lot of Verner Vinge's stuff is space opera - a Fire upon the Deep

The Altered Carbon Trilogy is pretty good too - check out Broken Angels/Woken Furies for more intergalactic bad-assery.

Oh and Forever War