If you have not read "Mote in the God's eye" and "The Gripping hand" you should do so now. Its one of the best first contact stories ever told, even though its set very late the Jerry Pournelle CoDominium universe (where USA and Soviet Union merged on Earth to form world government, which seems silly now), the pure space operaness of it is out of this world... It has jump points, ships with giant shields that take damage until they explode, diving inside the star to hide, space marines, psychic powers and and ... well read for yourself. Basically I feel like a lot of modern sci-fi literature and games like Eve Online or Stellaris can trace their origins to tech described in this series

P.S. Like John Ringo, Pournelle has a big hard-on for Sparta and/or Roman legions aesthetics, I think empire capital is even called New Sparta there.. Add Sparta/Rome in space + the great way Niven is able to write weird aliens, and you got a masterpiece