I read this in a thread where the person was already being corrected, so I feel awful mentioning it, but I keep related misuses of English and internally groaning about it, so I'm aiming this at people who don't know (and not at those who know but don't care) and sticking my head up over the parapet to do so.
...Must of read it wrong or something...
What was really meant was "Must
have read it wrong or something."
You see, there's a common abbreviation (especially in written speech) of "have" to "'ve" ("would have => would've"; "could have => could've"; and (in this case) "must have => must've"). In various accents/affectations this comes out closer to "ov" than "əv", which seems to be misunderstood as "of" by children learning their grammar and thenceforth perpetuated in speech and writing as the substitute preposition instead the original verb. (Yes, language mutates, but changing from a verb to an unrelated preposition is like losing a leg and gaining an ear in its place[1]. Hardly a constructive, logical or sensible change to language. IMHO, of course. IANALinguist.)
Anyway, whether you want to take note of this or not is purely up to you. Please excuse the vent. Also, you may well spot errors of my own, as incarnations of the Pedant's Curse. Two were deliberately left in[2], but who knows how many more exist!
[1] OK, so grasshoppers apparently have ears in their knees, it just occurred to me, but that doesn't invalidate the above simile.
[2] Not including my decision not to pedant the lack of the personal pronoun in the original quote. That would have been petty!!!