Is your feature request related to a problem? Please describe.
Nope

Describe the solution you'd like
Config value to allow tomeable items based on oredict/tag registration.

Describe alternatives you've considered
None

Additional context
I'd like to use minecraft:lectern_books since it appears a number of guidebooks fall under this tag.

Thanks for the suggestion. This feature has been added in Eccentric Tome 1.10.0. I didn't include the minecraft:lectern_books tag by default, because it seems to be used for many other non-guide books. But you're welcome to add it yourself in the config under include_item_tags

Give it a try and let me know what you think

Closing due to inactivity. Feel free to re-open if the issue wasn't fixed.