Versions: MC 1.18.2, ET 1.0.3

Description:
If a mod happens to include more than one book such as multiple guides for different aspects of the mod (e.g. Tinkers' Construct), or different variations of some tool book (e.g. Cooking for Blockheads), it is possible to craft an Eccentric Tome already containing one book from said mod with another book from it. However, rather than being appended onto the list of books from that mod, the first book instead gets overwritten by the new one, with no option to keep or recover the old one.

As a (somewhat late) disclaimer, I wasn't actually sure whether the intent of the mod was always to support multiple books from the same mod, though I just assumed it was and made this as a bug report. If this was never the intention then feel free to re-categorise it as a feature request if necessary.

Agreed, I've noticed this as well. Perhaps it's in how the books are registered...? I believe this also occurs with both books from Botania.

I'd intended to gracefully reject books that have already been added to the Tome (instead of just swallowing them). So, I'll leave this open as a bug.

Allowing multiple books is definitely a useful feature, but not a bug, so I'll open a separate issue for that.

This will be implemented in version 1.0.4, which I should be releasing soon.