The Thunder and Lightning

2 of my favorite series like this are: The Compleat McAndrew by Charles Sheffield. They are a series of short stories about an eccentric scientist who develops an "inertialess drive" and his pilot who just tries to keep him out of trouble. and The Thunder and Lightning series by John Varley. Kinda hard to describe the series since each book is fairly different. Both series involve sub light speed drives and mostly stay close to the solar system.