If you're intending to read Doc Smith's classic "Lensman" series, then so you should; but you should definitely start, not with "Triplanetary", but with Galactic Patrol
. Here's why.
Chronologically, the first Lensman story was Galactic Patrol
, serialised in Astounding Stories from 1937-38. This was followed by the next three stories: Gray Lensman
, Second Stage Lensmen
and Children of the Lens
. When publication in book form was mooted, Smith revised his earlier Triplanetary
to fit into the lensman universe, and wrote First Lensman
to form a bridge between that and "Galactic Patrol". Masters of the Vortex
, another unrelated story, was likewise modified.
I, and many others it seems, feel that the four books representing Smith's original conception are the essential ones, and the others are disposable ("Vortex", in particular, being a pot-boiler with virtually no relation to the others). Although "First Lensman" certainly has entertaining moments (as when Virgil Samms is almost deafened at a Rigellian construction site, because the Rigellians have no sense of hearing and can't understand what the problem is).
There's another problem with the books, although fortunately not an insuperable one. Smith's universe, although already huge at the outset of "Galactic Patrol", expands as the series progresses. Originally, the reader didn't discover the total significance of the struggles going on within it until the end of "Children". But the books (except, for some inscrutable reason, "Patrol") feature tacked-on and needless Forewords that give away the whole plot. I STRONGLY recommend first-time readers to skip these.
"Triplanetary" is not as good as "Patrol"; and if you start here you may be disappointed — possibly enough to stop reading! Neither is it "really" the first book. But most importantly, you'll run headfirst into plot-spoilers that wreck the tension of the story.
When you've finished "Children", by all means go back and read this.