Having said that, sometimes it's easiest to fill shelves with faux books. Dick Tabor (NY State) taught me his technique and was kind enough to share a bag of books with me. Along the way, I've also made books by covering blocks of wood with printed covers.
Then I discovered this technique. You start with an old magazine with a glued spine. Using a metal straight edge and a utility knife, you cut a strip of the spine. As you cut, the pages peel off and you just keep repeating your knife stroke until you've cut through the back cover.
And end up with this:
You can print your own covers or use commercial covers such as these:
I had a stack of magazines saved for this so I cut them down for future use and easier storage.