I just spent an entire morning reading Atomic Rockets.
I suggest that you do, too (even if it’s not morning). Check out the sidebar links.
Anything that starts out by deconstructing Heinlein’s “Torchships” is gonna be fantastic, in my book (even if the analysis is kind of depressing, in the end).
[I grew up on a diet of E E "Doc" Smith, John W Campbell, and a lot of Heinlein. I'm still a sucker for planet-bashing and all the presumably keen stuff you could do with high power vacuum tubes. We've lost something in the transistor age.]