Well, the crash report should speak for it self
crash_report.txt

It appears that is not all, there is a new error:
crash_report.txt

Hello, it looks like you are trying to use Bookshelf in a development environment without Mixin remapping enabled. This is required to load mixins using your development mappings of choice. You can see an example of this here.

Mod dependencies on Forge need to be deobfuscated for development environments. You should also be using the maven and not a mods folder on your system.

repositories {
    maven { 
      url 'https://maven.blamejared.com' 
    }
}

dependencies {

    implementation fg.deobf("net.darkhax.bookshelf:Bookshelf-Forge-1.19.3:17.0.2")
}