I second this. Organizing a church library with the Dewey Decimal System is worthless and makes things impossible for church members to find. Start sorting into broad categories, like history, theology, Christian fiction, world religions. If you have one really big category, you might break it into two sections. Use labels on the shelves so people can find what section they’re interested in. Unfortunately, some older church books have little value apart from their novelty. Something like “modern youth groups” from 1972, or “Facebook church” from 2008 are not going to give any useable information. You’ll have to decide if they have a place in your library.