This has been prosecuted criminally, in the scenario of people taking a huge pile of "free" newspapers to sell for recycling. See coverage in the Independent from 16 February 2019. Some previous prosecutions against the same or similar groups had been dropped but this one succeeded.
While copies of the Evening Standard are given away for free at train stations, the big stack of them is still somebody's property, and the socially expected arrangement is that a member of the public will take just one, rather than the lot. The reason they are being offered is to achieve a wide distribution among members of the public, and not because the owner simply wants to be rid of them, or wants to reward a random person with a minor recycling windfall. So, taking them in excess could intuitively be regarded as theft, because the person taking them is doing so in circumstances where the owner would not consent to the taking.
Beyond intuition, we have to look at the statutory definition,
A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it (Theft Act 1968, s.1(1)).
Clearly the newspapers are property, which belonged to another, and have been taken with no intention of returning them. The doubtful element in this instance was dishonesty, as other people in similar situations have argued that they genuinely believed they had the right to take the free goods. But when you are offered £30 to go to the box labeled "FREE - PLEASE TAKE ONE", and bundle the whole pile into the back of your van, it's hard to convince others that you thought there was nothing dodgy about it.
Books given away in a charity shop are just the same, since there's an understanding that the current owner is trying to distribute the books fairly, which is defeated if a single person swipes the lot.
As a civil matter, the corresponding tort is "conversion". A problem with pursuing a civil action is that the damages (the money you get back from somebody to make you whole after their wrongful deed) would generally be limited to the market value of the appropriated goods. For the newspapers, that's essentially 0p per copy from the retail value, or a few pennies per copy if we look at the cost to the newsagent of getting them in bulk. There is also a claim possible in unjust enrichment from the amount the thieves gained from the recycling, apparently £90 per load. It might be possible to argue for higher consequential damages based on the "value" of having copies of the Evening Standard in front of many tube travelers, but that seems pretty hard to quantify in a way that the Standard would be happy with declaring in public. (That also becomes subtle in that the publicity value is to the publisher, but the papers have been stolen from the newsagent, unless there is some sort of bailment arrangement. But we are drifting quite far from the original question.)
For the charity books there does not seem to be a commercial argument which would lead to a larger amount of money being involved. So although you might prevail in the civil case, the game still might not be worth the candle.
