Also of interest might be the treatment by Lev Landau in his Course on Theoretical Physics Volume 3: Quantum Mechanics - non-relativistic theory. Deriving the Born "postulate" is in Section7: "The wave function and measurements" in the most available 2nd edition (but it is admittedly a rather abbreviated derivation). I am not sure if that was in the original 1958 edition.
Quantum systems measuring other quantum systems is part & parcel of quantum computation. So that can lead to more clear thinking on (some of) these matters.
Quantum systems measuring other quantum systems is part & parcel of quantum computation. So that can lead to more clear thinking on (some of) these matters.