There must be a running joke between software developers that all slots that are 'Books Of' anything has to have exactly the gameplay mechanics.

Regardless of the reason, it results in Pragmatic Play’s Book of Vikings being a deeply unimpressive slot. We’ve seen the feature before in Book of Dead (and Book of Ra, and Book of Champions, and loads of other books!) and this title doesn’t bring anything new to the table. It’s a fine slot, but we feel like we’ve read this book before.