For reasons that I can't quite recall, I came across The Singular Universe and the Reality of Time, by Roberto Mangabeira Unger and Lee Smolin. RMU I only know because some idiot insists on puffing him up on wiki; but that did make me suspicious. LS, to me, is just a physicist of some repute.
So when in the CUP bookshop (one of the benefits of living in Cambridge) I spent perhaps 10-15 minutes browsing through it. For such a tome you will doubtless claim - or anyone supportive of the work would doubtless claim - that is far too short a time. Well, tough. I don't have all day.
The book is perhaps 2/3 RMU and 1/3 LS. The RMU section I found to be meaningless and thus worthless. I use those words literally; there was nothing of any value in there that I could find. Peter Woit reviews the book and says " I found the long section by RMU rather hard going and not very rewarding, and realized that I have a fundamental problem with this sort of writing. Arguments about physics and mathematics made in natural language leave me often unable to figure out exactly what is being claimed". Which I think is him saying the same, but more politely.
So let's move on to the LS section, without pausing to wonder - because the question is unanswerable - why LS is wasting his time associating with RMU. What I'm going to say - I promise - are my opinions, formed before I read PW. Also, in case you think PW is merely a professional rival of LS and dissing him, read his review of The Trouble With Physics (though he is less happy with more recent stuff).
I'm going to cheat though and copy PW's "three ideas" that LS has:
1. The uniqueness of the universe.
2. The reality of time.
3. Mathematics as the study of evoked relationships, inspired by observations of nature.
#1 is no multiverses. Well, meh. That's hardly a controversial viewpoint. Multiverse or not is a thing you can argue about, but there's no strong evidence either way. Quite how this fits together with his prior support for Cosmological natural selection, I don't know. I would have expected a section reconciling the two, but didn't see it.
#2 is also rather meh, in that to me it simply seems bleedin' obvious, and scanning of the book didn't reveal much in the way of deep insight from LS expounding his thesis. Somehow he hops from this to the idea that physical laws themselves evolve; as PW points out, this begs the question of what law they evolve according to. It would, I think, have been much better if anchored in experience: is there evidence, or conceivable evidence, for the truth or otherwise of this proposition? LS seems to have gone the string theory route of speculation without evidence.
#3 was hard for me to make any sense of. PW points me to a shorter essay which may be about the same thing, from which I quote "My aim in this essay is to propose a conception of mathematics that is fully consonantwith naturalism. By that I mean the hypothesis that everything that exists is part of thenatural world, which makes up a unitary whole... If, on the other hand, all that exists is physical reality then mathematical knowledgemust be an aspect of knowledge about physical reality...". That doesn't make sense to me. PW's comment is "In his essay, Smolin gives a discussion of mathematics itself which I think few mathematicians would recognize..." and you should read him for more if you're interested.
I poked around for some other reviews and found Goodreads.
* Manny: "I am a fan of Lee Smolin, so it pains me to say that this one was a major disappointment... even if it's wrong it asks so many interesting questions that it's absolutely worth reading. The problem is that most of it appeared in Smolin's last book, Time Reborn"
* G R Reader: "Roberto, why don't you come clean and admit what's as plain as day? You ran out of ideas; you tried to solve the problem by repeating yourself ad nauseam with minor stylistic variations; CUP refused to publish the result; Lee came in at the last minute and saved you by writing (more accurately, cutting and pasting) 150 pages in a couple of weeks; it was then accepted with very bad grace; the final product still stinks."