[DuncanWatson]

So with other e-readers implementing collections of some type, you might wonder how to manage your books on the Nook. I am a new user myself but I did discover some options using Calibre and a soft-rooted nook with the updated nookdev NookLibrary app.
(note all links go to either nookdevs.com, mobileread.com or flickr)

First how do you get this installed.
Step 1, Softroot your nook. Instructions here
Step 2, update the NookLibrary app and possibly the NookLauncher. Instructions here
Step 3, Install Calibre on your computer from here

Now you have the basics.

I use Calibre to manage sideloaded content and the My Books app in the softrooted nook to view it. I find Calibre very useful, it allows me to assign ratings and modify the metadata of each book. The most important part of this for the purpose of this topic is the ability to add and manipulate "Tags" in Calibre. I have added tags to a number of the ebooks in my library. Here is a view of some of my ebooks in Calibre and how it looks. Click through the small image for a larger version (on flickr).


Once you set up a few tags you can use the NookLibrary "My Books" app to limit the display of books in your library to just those with a given tag. I don't have a picture of this just yet but I will edit the post to show one later (my wife is out of town with the digital camera).
The basic instructions are to go to the "My Books" app, then scroll the lcd screen up so you can see the button labelled "Show". It will default to a selection of "All" which will be next to the "Show" label. If you select it, the LCD will now give you a list of all of your tags, select one and limit the list of books above in the e-ink display to just the books that possess your tag. In my case I might select "Fantasy" to see all the books I have that are tagged with Fantasy or Science Fiction to limit the display to science fiction. I could also tag all books that are part of a series with the series title, such as Belisarius, to limit my books to the series by David Drake and Eric Flint.

Another useful trick is to limit books to a given author. This can be accomplished by use of the Author button in the same app, located just under the "Show" button. To reset this to default behavior you go to to each button and select "All" and you will now see all of your books.

Now because B&N books are loaded directly onto your nook and aren't managed via Calibre, this might seem a wee bit useless. How can you control and manage the tags without Calibre? Well the answer is not perfect but it is possible.

Here the process overview.

1. Import each B&N book from your nook into Calibre.
2. Edit the tags and metadata in Calibre to suit your needs.
3. Transfer the books from Calibre to your nook (sideload).
4. Hide the B&N version of the book from "My Books" using the archive button.

1- Import each B&N book from your nook into Calibre.
This is relatively simple.
a. Connect your nook to your PC while Calibre is running.
b. Navigate to the nook drive with your file browser. I use linux and it looks like this:

I enter the My B&N Downloads and see this:

c. Select all the epubs on your nook.
d. import them into Calibre.

I have my OS configured to launch epubs into Calibre and Calibre auto imports them. This step may require you to do the same for which ever OS you run. You may be able to get the same effect by right clicking the selected ebooks and "open with" the selection with Calibre.

e. Wait for Calibre to "add" each of the books into its library.
2- Edit the tags to your hearts desire.
a. Too many tags is as much trouble as too few. I try to have some control though it is easy to get carried away. The choice of what your tags are is up to you.
b. Select an book in the Calibre Library.
c. Click on the "Edit Metadata" button in the Calibre menu.
d. The 6th item in the dialog box is the "Tags" Edit Box. Tags are comma separated and just text, they can contain any valid text characters. I suspect with the current software version of the Nook this is limited to Latin character sets if you want to see it display on the nook properly.
e. Go through each of your books and add the tags you want. You can also use the bulk edit method by selecting multiple books. If you do this you can only add tags, you can't change tags or delete them.
3- Sideload the content from your library in Calibre to your nook.
a- connect the nook via USB.
b- select your books in Calibre
c- click "Send to Device" in the Calibre menu.
4- Hide the B&N version of the book from "My Books" using the archive button.
This is the tricky part.
a. Go to the B&N launcher in your nook.
b. select the "My Library" button.
c. Make sure it is viewing "My B&N Library"
c. select the "View Item Details & Options" button in the LCD display while your desired book is selected.
d. You should see the book cover, Read, Lend, some stars, and View buttons on the LCD.
e. scroll the LCD up so you can see the "Archive" button.
f. Select the Archive button
g. your book is now archived and hidden from the default launcher.

Now that you have gone though this admittedly long process you now have sideloaded a B&N book with your custom metadata and hidden the B&N version of the same. You should now have only one version of the book visible in your "My Books" library and you can treat tags as collections.

I hope this helps, and I am sure some posters will post corrections and easier ways to accomplish the same results.
-Duncan