What's the Downside?

I'm reading a Peter F Hamilton book right now. His work isn't perfect, but I like it. He achieves a fairly staggering level of scale, whilst corralling a considerable number of characters who are worth your time^[1] and develop naturally, if exceptionally. His books are, however, frikkin' gigantic. This one is 725 pages long, and is shorter than a lot of his other work. It's not ideal for reading on journeys, and you wouldn't want to pack more than one of them for a long trip. It's also not like PFH is the only long winded author I read. See also Robyn Hobb, Neal Stephenson and Brandon Sanderson. I don't only read huge Sci-Fi/Fantasy epics, but I do often read them.

Additionally, I have stacks and stacks of books, even taking into account that I divested myself of a lot before leaving Edinburgh. When I move into my new flat^[1:1], I'm not sure I'm going to have space for them. If I could stop that collection growing too much, that would be ideal, but I have no plans to stop reading or buying new reading material.

On the surface, to me at least, the ideal solution to this would be a kindle (or, I suppose, some other eBook reader). All of a sudden, Pandora's Star is now the same Size as Cat's Cradle. Crytonomicon is the same size as Memoirs of a Geisha. Plus, it doesn't matter how far I'm traveling or how little space I have, i can basically pack as many books as I'd like. Likewise, the book collections would not (physically) expand in size.

But what about the books I have already? Do I just keep them, rammed onto the shelf space I have? Do I instead charity shop^[1:2] them? Do I replace / duplicate some or all of them with the eBook version? There's no ideal solution here.

The publisher is never going to give you the eBook just because because you own the paper copy, and likewise I suspect the majority of people of aren't going to want to pay full price for an eBook they already own. Plus, books are not quite so easy to format shift as CDs.
So, here's what I propose: you take your book to a shop and pay them a nominal fee (say £1). They then give you the eBook version of your book, in the format of your choice. The book itself gets recycled. The shop and the publisher then split both the cash and the revenue from the recycling. You've format shifted your book, with only a small outlay. The publisher has benefited from this transaction. No new copies of the book have been magicked into existence (also good for the publisher). Lastly, raw material for recycled paper has been obtained. What's the downside?