I just released an update to BiblioCraft, making it version 1.11.7 now for Minecraft v1.7.10. This update fixes a crash that occurs when you try to start a deticated server with BiblioCraft v1.11.6. There was a bug I introduced on accident in the last update when I fixed a dupe with the slotted book. I forgot make the call to open the gui happen only on the client and let it happen on the server where it should never happy. That is fixed now in this update.
Head on over to the downloads page to grab a copy. Enjoy!