I recognize this bug as BetterQuestingTriggerer had this issue for a while too.

The book is opening the Better Questing GUI twice, probably due to a handedness issue. You can tell because you need to click the Exit button in the menu twice when accessed via the book.

Looks like I have the fix for it, I just need to test it against multiplayer and update the book image. Then I can release an update for 1.10. Should be available tomorrow afternoon.

Version 2.1.0-1.10 has been released and approved. This issued should be addressed, unless you dual wield quest books. I will be opening a new issue to track better internal handling for that very slim edge case.