In that case you are connected to the content server and have not yet downloaded the book you are trying to read.
You can tell you are connected to the content server because before tapping on a book to see its details, the action bar says "CC Content Server". If you are connected to the content server, the page displaying books will have a check mark next to the book if the book is downloaded. See the screen capture below.
You should tap the "back" button until you disconnect from the content server. At that point you will see only books you have already downloaded, not books that are available for downloading from your calibre server.
Edit: Assuming that you have downloaded books, once you have disconnected from the content server you will also be able to use CC's grouping, sorting, and searching facilities.
Edit 2: You might want to try connecting as a wireless device. This mode is far better for doing bulk downloads than the content server. Once connected, you can use calibre to "send to device" the books you want on your tablet, and can use calibre's books-on-device display to bulk delete books from your tablet..
Last edited by chaley; 11-26-2012 at 07:20 PM.