More solo pub talk. I am tempted to suggest that the person who reads a book in the gentle afternoon of a quiet pub is a generous soul, happy to pass the time in a public space with the ebb and flow of humanity around them (otherwise they’d have bought a bottle of sherry and sat at home). Conversely, he whose reading habits take up a whole table in the context of a busy pub is a cruel man (possibly a psychopath) with no regard for his fellows.
But of course, it’s more complicated than that. If, for example, you see someone sitting on their own at any time reading a Tom Sharpe novel then leave the premises immediately: they are up to no good and their brain is most likely a scrambled rictus of hatred. If you see someone reading a hobby-related magazine (Anglers’ Monthly, perhaps, or Record Collector) then they are probably self-absorbed but harmless. Be aware, though, that they may be the advance guard of some sort of meeting of like-minded souls. I once frequented a lovely bar which became unusable fortnightly due to the appearance of a live role-playing / sealed knot style group.
As for offensive behaviour, I think very loud walkman use would fall into this category, as would ostentatious self-grooming such as toe-picking or nose-picking. If a stranger asks to read a single section of my Sunday paper, that’s fine (assuming they return it when they’ve finished): asking to read subsequent sections would get my goat. Buy your own! The newsagent is only just down the road!