Another Ace Double

I have in my possession an Ace Double book published in New York in 1959. On one side is The War Of Two Worlds by Poul Anderson, described on the cover as a "Complete Novel." Additional cover blurb declares, "Earth Must Choose - The Martians Or The Monsters!" The cover illustration shows four streamlined air- or spacecraft, two flying past, one being shot down by an Earthman with a futuristic hand weapon, the fourth already crashed on the rocky terrain.

Inside the cover:

p. 1 summarizes the plot and advises "Turn this book over for second complete novel";
p. 2 is a "CAST OF CHARACTERS";
p. 3 is the title page for The War Of Two Worlds;
p. 4 is the publishing details;
pp. 5-108 are the text of novel.

Thus, this novel fills 104 pages. A novel is a long prose fiction. My rule of thumb for a novel is 100+ pages so this work qualifies. I read it once on purchase years ago and will reread it to blog.

On the other side is Threshold Of Eternity by John Brunner, "Complete & Unabridged." Cover blurb informs us that "All Time And Space Was Their Battlefield." The cover shows a giant in a gas mask tearing through a wall, knocking over machines and threatening four space-suited men, two of them armed.

p. 1 summarizes the plot and advises "Turn this book over for second complete novel";
p. 2 presents information about the author;
p. 3 is the title page;
p. 4 is the publishing details;
pp. 5-148 are the text.

I have not read Threshold Of Eternity but will because:

I have not read much Brunner but know that he could write well;

I am particularly interested in time travel although I found Brunner's Times Without Number disappointingly incoherent (about a time travel organization but in no way comparable to Anderson's Time Patrol series);

I will compare Threshold Of Eternity with Anderson's works about conflicts through time and comment either here or on the Logic of Time Travel blog.