Buying a house from a homeowner gives no money to the original builder, or the first human being to inhabit that piece of land. Do you feel guilty about getting shelter without paying the price of admission?
I think this is a disingenuous comparison. Builders get paid to build houses. Authors, to my knowledge, do not frequently get paid to write books, they get paid when they sell books.
When you resell a house, you are not denying the builders anything. When you resell a book, you are (possibly) denying the author a sale.
> When you resell a house, you are not denying the builders anything
You're denying the builder a sale of a new house.
Re-selling books is already legal. You bought a physical item, not the right to use the item. Ownership implies the right to dispose of the item as one wishes. You asked whether it was morally correct. I was showing you that many other things are frequently resold with no moral implications.
When you resell a house, you are not denying the builders anything. When you resell a book, you are (possibly) denying the author a sale.