error message in books: says it can't open the book because there is a problem with iTunes

I was able to read my book in April 2020, but now when I try to open it in my mac's 'Books' app, I get this message: "This book can't be opened. There is a problem with iTunes (--42408). Reinstall iTunes, then try again." Why the heck is this happening?

My Books app is v1.19(1645), my iTunes app v12.9.5; both are up-to-date for my mac which is running macOS Mojave v10.14.6 (I can't update to Catalina or higher because my MS Office for mac 2011 will stop functioning)