Why can I not access a book I paid for years ago until I update my payment info?

If the book is already fully downloaded, I’d expect it to open. But if Books needs to download or reauthorize it, an unpaid balance on your Apple Account can block that.

I’d check Settings > your name > Media & Purchases > View Account > Purchase History and look for an item shown in red as Amount You Owe. Apple says you can clear an unpaid balance with another payment method or, where available, Apple Account credit from a gift card.

That may be useful while you’re waiting for the replacement credit card:

If a message says 'billing problem with previous purchase' or 'verification required' - Apple Support

If the book is definitely downloaded to the device and still won’t open, I’d contact Apple Support rather than buy it again.

Eric Trueheart wrote:

It's still frustrating that I can't read something I've paid for simply because I need to download it.

There are two ways to view the content purchased, either download it where it will always be available on your device, and also use it's storage, or leave it on Apple servers where you are going to need your account in "good standing" in order to access the Store. Currently your account has been disabled because you have a previous purchase that has not been paid.

It works the same way for the apps on your device, where you can continue to use the apps that are downloaded to the device, but with a Disabled Apple Account, you would not be able to use the store to redownload any of the apps you have previously installed, whether they are paid apps or not.