Thanks Harry - that's at least part of the problem.
I've checked and all the books that do this haven't been indexed on the Voyage.
After working to correct it I can eventually get all of the "Search This Book"s to work, though by sometimes strange means. Some will work after re-downloading and giving them time to index, while others will work, oddly enough, only after using the internet on the Voyage (such as by going to goodreads through the "g"). About This Book on first opening is still not working on any of these.
There seems to be a distinct difference here - books that never had these problems seem to index and are ready basically right away while these books need more time or special goading for Search This Book to work while About This Book on first open still doesn't happen.