At this point, I would go ahead and send it in. There's a good chance that whatever you ship now won't be fully available until after Xmas; my typical experience is that a shipment gets received, then sent out to other FCs, so not available for sometimes up to 3-4 weeks.

And for me at least, January is a good month for books, then it typically drops of pretty radically. So you don't want to miss that window (of course, it will vary on what you sell; I can only report based on my personal experience).

And while last year was an exception, in the past, January has done especially well for Self-improvement and diet books.

I would also advise not to send anything with a sales rank over 1M; keeping it under 500K is even better. Storage and (especially) removal fees can take a big chunk out of your bottom line.