This set of older first grade books I have can not be replaced. The reader can be reused easily, but the workbook was meant to be consumable.
To solve the problem, I folded the workbook in half and slid a clear page protector (found @ Walmart in office supplies) over it. I have the children fill it out with a dry erase marker.
This not only saves money, but allows us to use the materials we like the best regardless of when they were published.