So long story short, the UK hardcover for 'Let the Right One In' is now OOP and it's the only hardcover with the correct English title translation (the US edition being 'Let Me In'). I don't know how 'valuable' it is as some have sold it for $25 while it's gone from $50 to over a hundred elsewhere.

Regardless it's one of my favorite novels and I was lucky to find a slightly dinged copy for very cheap. I recently got it a brodart cover and slipcase from Jeff Whiley for it. I suppose such protection is unnecessary for a book that's already used but if I ever come across one in better condition at least I'll have something ready.