Replacement books are something around $25 apiece. It's not a huge price all things considered. Personally I would either replace yours or just use the digital textbook on the online course (which will be up to date). Reg will certainly need to be replaced – your textbook is probably pre-TCJA. I would only order one section's replacement at a time though – more updates are coming this summer and then in December.
AUD - 94 BEC - NINJA in Training FAR - 95 REG - NINJA in Training