I wanted to share what I have discovered. It is an app called Calibre Companion. ($2.99 google play store).

If you like to read on a tablet that has google play, and you are a user of Calibre on your computer, this app was made for you!

I can not express how great this app is. I have it on my Nook HD. I bought that tablet for reading, and just attaching it to my computer to use Calibre did not work the way I wanted. So I saved books to a file on my computer and dragged them over that way, or downloaded from Copy or Drobox.

No more! I installed Calibre Companion, and it was super easy to connect wirelessly with Calibre. Then I sent some books from Calibre wirelessly to the Nook. They show in the CC app with the series name and number. I noticed some covers were missing, but when I synced back and forth among my Calibre libraries, they all showed up.

THEN I noticed that all the books I had previously loaded onto the Nook, ALSO show in the CC app! Awesome!

And the real clincher! Library management. You can easily find what you want. You can sort by author, title, series, and TAG. I can change tags on my computer, and next time I connect CC, it automatically applies the change to my on device library!  I can go to R, and all the authors whose last name start with R, are grouped together. Click on a title, and you get a page that shows the book description. From there you can choose "read" and it will open in the reading app (I am using Cool Reader now).

This is a big time saver for me. It was SO worth $3! It will work on most any android tablet, but not on a stock Kindle Fire, from what I understand. I have it on my n2a Fire HD and it works great.

I now have over 4000 books on my Nook HD, it is truly a reading tablet now!

I've been playing with it a bit, and so far it's really nice. It'll be a bit before I can load it up and see if it can handle all my stuff. Lol. 

I like it, because it satisfies my need to stuff as many books as I can onto a device. Now I can do it on the Nook and leave my Kobos alone LOL

It took me a little more effort to get it working with my Android tablet, which I use primarily as an e-reader. But finally did and definitely enjoy the benefits.

That's great, Jo! I am enjoying my Nook HD more than ever, now. It's my favorite reader at the moment.