Law of propability: I had zero dataloses due to fire, some data loss due to loosing a thumb drive backup and some data losses due to cloud storage shennenigans.
Hmm. I highly recommend a three way redundancy as others have mentioned. Put a copy in the cloud or store your harddisks somewhere else.
You are right, a cloud storage would make things a tad saver. Personally, I made a point in not putting anything in the cloud, especially none of the big providers, since I value my privacy and just don't trust any o those companies.
Create a new backup from the cloud provider one. Vice-versa if the cloud provider backup gets lost. Chances of loosing both at the same are minuscule.
For the really important digital stuff (almost 30 years of family digital photography and video and some paperwork) I have a rotating backup schedule. Two of the drives in the rotation stay at my mother's place. Nothing fancy and it's mostly when I can bother to remember. About once a year or so. Still, some peace of mind.
I do both, personally. Have everything on my HD and on the Google cloud. That seems like an appropriate level of redundancy.
A photo book doesn't sound much better for that either.