It's good, but for some reason (unclear to me) Ballentine never mentions decoherence. For example, after Eq. (9.13) he says:I think chapter 9 of Ballentine is a good place to get introduced to this stuff.
"It is clear that the nondiagonal terms in (9.13) cannot vanish so as to reduce the state to the form of (9.12) ..."
At this point nothing would be more natural than to mention that decoherence provides a FAPP mechanism to arrive at (9.12). Yet, for some reason, Ballentine does not say anything of that sort. Do you have any idea what his reasons might be?