[radius]

Have you experimented using a single folder? That might be faster and easier (ie: you know the indexing finishes almost instantly if the folder only has a couple of epubs in it).

I did this and it worked for me:

1) Downloaded v1.8 of the mdimporter, unzipped it and put it in the /Library/Spotlight folder
2) Opened a terminal and used the following command: "mdimport -r /Library/Spotlight/epub.mdimporter"
3) Put some epubs in a folder
4) Opened system preferences and went to the privacy tab of the Spotlight prefs. Added that new folder as a "do not index" and then removed it again to force an indexing of my new test folder.
5) did a Spotlight search for the word "protomolecule" and up popped Tiamat's Wrath in my search results.