First Lensman by E. E. Smith
I was persuaded to try First Lensman in spite of not being well impressed with the Best Of E. E. Smith. The premise of the Lensman series is that a race of “bad” aliens of great power has come from another universe to conquer ours. In our universe there is an ancient powerful alien species that is not precisely "good" but have their reasons to oppose the incoming bad aliens, and intend to oppose them in a way that will in effect be beneficial to humans and other less powerful peoples. For one reason or another, the two powerful alien races choose to work through the actions of the less powerful races. The "good" aliens give certain humans of good character a "lens" - an "indistinguishable from magic" gizmo that lets them communicate telepathically faster than light and such.
First Lensman is the second volume of the Lensman series. However, even those who like the Lensman series in general often suggest one not bother reading the first book, Triplanetary. First Lensman is also the first book in the series in which the good aliens start providing "lenses" to humans and other less powerful races. The book has a few parts to it. There is talk of plans by some humans to build an interstellar police / military force to defend all that is good and wholesome. There are a couple of parts which may appeal to readers of military SF. The longest plot segment is more along the lines of espionage SF. In this part, the good humans (with a few good individuals from other planets) are trying to collect the evidence to follow the trail of an illegal drug from plant harvesting to processing, through circuitous transportation and distribution. In this sense it's not espionage in the usual nation-vs.-nation conflict.
While I found First Lensman is generally not to my taste, I can see an aspect in it that would appeal to some readers.
The writing style leaves much to be desired - and considering the fact that writing style is not my top priority in SF, I imagine readers who do focus more on style would have more issues with Smith's books. The plot and dialog make me think of comic books in my youth. It's not quite what I think of as "literature" - and, again, I'm not such a high-brow sort. The kind of hard SF which is criticized for lack of character development is not such an issue for me - and that hard SF strikes me as more literate than Smith.
As readers of my reviews may know, telepathy (especially between members of races from different planets) is one of my pet peeves. The "lens" is a device of extremely hi-tech. Perhaps, a sufficiently advanced civilization could produce a translation system that would allow communications between members of any two species whose translation needs had been previously established. However, the "lens" seems to be able to provide communication with members of species whose translation needs have not been previously established - and with the "lens" being worn by only one of the individuals involved in the communication. This is not very convincing to me.