Reading material unpacked, leaves the hotel (5,3)

I believe the answer is:

books out

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'hotel' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'reading material unpacked leaves the' is the wordplay.
'reading material' becomes 'book'.
'unpacked leaves' becomes 'sou' (I can't explain this - if you can you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'book'+'sou'+'t'='BOOKS OUT'

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I've seen this clue in the Evening Standard.

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