This is hard SF at its hardest. The first half of the novel is essentially a documentary of the work of various high energy physicists at the SSC -- the Superconducting Super Collider -- accelerator in Texas. But in the background we know something nasty is about to happen: the SSC reaches high enough energies to attract the attention of other bubble universes: a behind-the-scenes race is on for the Makers to contact us before the inimical Hive Mind does. First Contact doesn't happen until about half way through the book, and by then I was getting a little impatient for something SFnal to happen -- it was essentially techno-thriller up until that point. But when contact happens, all hell breaks loose, and things get very exciting very quickly.
As well as the plot development starting off rather slowly, Cramer's style is rather flat: I never did manage to distinguish the two main characters, George and Roger. And the characters do tend to talk text-book paragraphs at each other. But the plot, once it does get going, is fascinating, with a great twist taking it off in an unexpected direction that caught me entirely by surprise. The SSC physics is right, and even the SF physics later on is all solid extrapolation of stuff known today. (Cheekily, Cramer gets the advanced Makers to laugh at our Copenhagen and Many Worlds interpretations of QM, wondering how we humans came up with such strange ideas as well as the obviously correct Transactional interpretation: Cramer's own Real World work! But even that is not nearly as cheeky as his interpretation of events surrounding the SSC's construction.) Some of the background material is available on the Web.
If the first half background had been a little shorter, with instead more of the second half's SFnal content, I would have awarded this a 2.5, despite the flat style.
Maybe two or three years ago, I bought John Cramer's novel Einstein's Bridge.
Before getting around to reading it, I read a review of it on your website. You mentioned, "Cramer's style is rather flat: I never did manage to distinguish the two main characters, George and Roger."
As a result, when I did read the novel, in addition to experiencing the usual pleasures thereof, I also played the game of trying to find differences between the two lead characters, George and Roger.
Some characteristics are dificult to specify in a way that permits precise measurement. For example, there's something a bit vague about degree of willingness to risk one's life in order to achieve a difficult goal.
One of the (more trivial, but objective) candidate characteristics I found was a habit of stroking one's chin, which initially seemed to be a habit of one character but not the other.
You might be interested to know that among other references:
page 95:
[Roger strokes his chin, Susan comments on it.]
"'You always stroke your chin when you're thnking hard,' she said. 'Elvis [a rhesus monkey] seems to be imitating you. Perhaps he's thinking of going into particle theory.'"page 168:
"George stroked his beard..."
DAMN! HERE FOR A LONG TIME I THOUGHT I'D FOUND A DIFFERENCE BETWEEN THE CHARACTERS!page 177:
"George stroked his beard for a long time." [emphasis added]page 187:
"George stroked his beard, frowning." [emphasis added]page 226:
"Roger stroked his chin."
[So the difference is that Roger strokes his chin; George strokes his beard?]page 234:
"Perhaps it was the gray beard? He [Roger] pressed his chin again, reassuring himself that it would remain in place."
[What?! Now George and Roger are both beard strokers?]
I submit the hypothesis that the characters are strongly affected by a mysterious phenomenon that causes them to take on each other's habits, at least so far as beard stroking. I further suggest that in a sequel, Susan might be expected to grow a beard and take on the habit of stroking it.
