E. E. Smith's Lensman series, which begins here, is a classic of pulp science fiction. It's one I grew up with, several decades after its first appearance. It's a great, fun series, but only if taken in the context of its time - the leadup to World War II, and a time with very different values than we enjoy today. The women are smart, plucky, and essentially decorative. The men are strong, brilliant, and brave. Most moral decisions are clearcut, and when they aren't, the way forward is nonetheless obvious. Government is good and always acting for the best.
The two powerful races that start the story (in epically dense prose), the Eddoreans and the Arisians, encapsulate the ethos perfectly. The Eddoreans are selfish, arrogant, greedy - the epitome of everything cruel and evil. The Arisians are wise, generous, kind - they can do no wrong, even as they see their own shortcomings and plan for a stronger successor. That's pretty much the style of the series, and certainly of this first book (retrofitted to the series when novelized) - you'll never be in much doubt as to whom to root for. There's an attractive simplicity to that. In a time when we are blessed with SFF characters who travel in shades of grey, it can be relaxing to return to a series where good is good, and that's all there is to it.
The sexism in the series is a pervasive product of its time. It's not as easy to settle into that aspect of the book, but give Smith the benefit of his time, and focus more on the plot action, and you'll get past it. The characters here aren't deep - they're staunch and loyal, and they always do the right thing. It's the tractor beams and blaster fire that are important.
I'd forgotten just how rapidly the technology develops here. I could have sworn that shears and pressors and the inertialess drive took much longer to emerge, but they all come in right in this first book, seemingly developed over a matter of weeks by geniuses who need only one look at an enemy's polycyclic shield to immediately understand both its foundational principles, and the technology needed to go it one better.
Again, though, the Lensman series is not about credibility. It's about good beating evil. That was something people needed to hear in the middle of the last century. It's something we can stand to dream about again now. If you haven't read this series, you should. It's Science Fiction 101, and if you read it as a creature of its time, it's a lot of fun.