Shame the Touch HD is stuck at firmware 5.x (the Verse is 6.x). Provided the firmwares are equal, you could try(!) to copy all the book files, and then both databases (explorer.db + books.db).
Even with matching firmwares this is not guaranteed to work, if the databases somehow differ between devices. Might even brick it... I'd at least clear the newer device to be safe. Right now it will fail as the database formats differ between firmwares 5 and 6,
so don't try it!
In theory, a HD3 could be used as an in-between, brought down to 5.19.656 to match the Touch, and then upgraded to 6.8.2102 - the HD3 and Verse firmware version don't equate exactly however there. PB developers ought to have update scripts for databases, but I doubt they'll spend time on this
BTW, there's an unreleased GUI tool for my AVATeR, that transfers read states+percentages between two devices. It's unpublished as I felt it could break and cause more trouble than it was worth. Might brush it off, in time.