A E van Vogt's "The Wizard of Linn" (novel, space opera, free): We live in a recursive universe!

This is the last of author's half dozen odd stories comprising "Lord Clane of Linn" series, & the strongest of the lot. This is the only novel in the series; all others are short stories.

Caution: It took me a while to get into the unbelievable series. A feudal human civilization where you travel by horses & fight with arrows, spears, & swords, but with pockets that have inherited technology way beyond anything we can think of - technology that is used without understanding. And a superhero who achieves technological advancement - working intellectually alone - that is equivalent of thousands of years of normal human progress!

Story summary.

Riss, aliens who had completely destroyed human star-faring civilization in a war 5000 years ago, have returned to Sol with the intention of colonization - destroying humanity in the process.

And their opposition is humanity distributed across several worlds of Sol, the most powerful of which is earth. Earth has feudal Linn family for rulers - a family that is always assassinating a member or another of its own in interminable power struggles, not to speak of general misrule.

The task of saving humanity, as also putting it back on path to technological advancement, rests of Lord Clane, the despised & feared but very capable mutant of the ruling Linn family. Of course, he will succeed, & in only a few years - after a lot of drama & killings. In the process, we visit isolated human worlds on 2 other star systems - one an agricultural society that takes teleporting & telepathy for granted, another where man has burrowed underground but possesses a superweapon he doesn't know how to use.

Major weapons.

1. A "sphere" or "ball" that's actually our whole universe, contained within a few inches! Not a copy, but the same universe! This sphere operates with telepathy, can be sent to do some destruction or to absorb energy of a blast in defense. And with right equipment, when you hit a certain area of a certain "world" within this miniature copy of the universe, the real corresponding world is hit with matching ferocity - because they are the same!
   
   Greg Egan's "Dark Integers" has a similar idea - whenever a certain integer variable that is part of the definition of a computer program acquires certain "bad" values during some run on any computer, bad things happen in a parallel universe!
   
   Essential idea itself, of course, is very old - remember the (I think) Arabian Nights' story of magician whose life is in a parrot kept elsewhere, or Ramayan's story about Ravan's life force living in his naval? May be all kinds of switches have their origins in such tales!
   
2. An energy field that can protect a volume of space from all intruders except those on a white list. Individuals on white list must be identified to the system via a biometric "photograph". Anyone not on this list gets cooked on entry.
3. "Molecular weapons" that can protect a volume of space from even atom bombs, acting as a protective shield.

Fact sheet.

First published: As a 3-part serial in Astounding, April/May/June 1950.
Rating: B.
Download full text from Baen CD.
Quotes from this novel.
Listed among the stories from John Campbell's Astounding/Analog.
Related: Stories of A E van Vogt.