Fra,
I've seen the paperback *really* cheap, and the one with the blue cover has good binding... and that is the right book, yes.
As to whether Penrose's book is a "pop sci" book, it depends on how you define that. Penrose's goal seems to have been to write a "serious science" book for a popular audience. He says early on that he's trying to write for multiple levels at once, such that the material is detailed enough that someone with heavy physics experience will still learn new things, but someone with no background will at least understand the general idea of the material presented (even if the details interesting to the experienced person sail over their head). It is a difficult tightrope to walk but he gets away with a lot of this because he actually does attempt to present *ALL* of physics-- when he says "A Complete Guide to the Laws of the Universe", he means it. Because he does this, he is able to "ramp" the material such that the concepts needed to understand the later sections would have been presented to the low-end readers in the earlier sections. (And he does not take compromises in how he does this-- literally the
first half of the book is just math.) Surprisingly the "basic" sections are a worthwhile read even to someone who already knows the material well, both because of the clarity of the presentation and because he chooses to focus on occasionally unusual details of those basic topics. (For example as I remember the first chapter in the "math" section is about noneuclidean spaces and the difference between dS and AdS-- a choice illustrative of how Penrose proceeds throughout, since it's not something you'd think of as something a popular science book would include at all, much less as its first example of "basic math material", but which if you think about it actually is both fairly relevant to modern physics and fairly easy to strip down to accessible essentials). For this reason though it *is* a "massive" book. Again though it's largely written to be clear and concise so it's a somewhat quicker read in places than you'd expect.
I've got a feeling Penrose tries to explain decoherence using gravity? or something thereabout?
So, I've only seen what of this idea that Penrose included in Road to Reality. But when it showed up there the idea basically worked like this: Penrose tried to depict quantum mechanics as consisting of two "operations", a U operation and a D operation (I think it was D). The U operation is the familiar unitary evolution of the schrodringer equation; the D operation corresponds to "waveform collapse". Quantum physics, as Penrose looks at it in RtR, is all about the U operation, but the D operation does
happen. This is a fairly copenhageny way of looking at things, and as far as I remember Penrose does not specifically explore the more complex picture of collapse painted by decoherence. I don't know whether this is because he would view decoherence as the D operation in little tiny steps or because he was oversimplifying for purposes of the book.
Anyway, at some point he suggests the idea that if we ask the question of what precisely inspires the "D" type operation to happen, the answer might be gravity: since GR requires mass to be in one place rather than a cloud of probabilities, maybe what happens is that the probabilities are allowed to spread unitarily until a moment comes at which one particular state is needed in order to "solve some problem" having to do with gravity, at which point collapse occurs. So we've got kind of a realist interpretation of the copenhagen interpretation: There's a quantum apparatus and a classical observer, but
the "observer" is gravity, since after all in one way of looking at things gravity is the only classical thing in physics. It was kind of an interesting idea, though I may be garbling or oversimplifying it here-- It was unclear to me just from RtR how seriously Penrose took this idea, and I don't remember if he offered any reason to think it might be true beyond "well, here's two things we don't understand, therefore maybe they're linked".
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One more thing Fra, just since you're reading Rovelli and such it occurs to me you
really should read
Roger Penrose's 1971 paper here which
John Baez recently finally posted to the internet, since it is the paper where spin networks were invented! As far as I know Penrose eventually abandoned the ideas from that paper and they weren't a part of his later thinking-- I think he mentions the idea of a combinatoric spacetime in RtR but doesn't explore it much further-- but the ideas in that paper do seem to have been fairly influential on LQG, and there is notation I have seen used by Rovelli and Smolin but which I did not actually understand until I read that paper.
