Updating means that it needs to reload the package list to get the most
recent versions. I am not a Software Centre fan so I cannot tell you how to
refresh the list. I don't like the way that it works and it provides too
little information. If I ask it to install an application for example and it
uses Mono which I don't want, there is no way of knowing. It just installs
it, no questions asked. I think that it is brain dead. I even searched
Ubuntu's help site and it does not say how to reload the package list from
Software Centre.

I prefer Synaptic or apt-get. :)

Method One:

Open a terminal and type: sudo apt-get update [press enter]
Type your password and press enter

It will load the package lists for software sources. It will now work in all
package managers using the updated lists.

While you are there you can then install Calibre (pronounced Caliber, like
the Dodge car or a bullet). to do that type: sudo apt-get install calibre
[enter]

Method Two:

Open Update Manager and hit the Check button. Close it unless you want to
upgrade packages to newest versions.

Method three:

Open Synaptic (if it is installed, no longer installed by default in
Maverick)
Hit the Reload button.

Once it does its thing you can install Calibre by Hitting the Search button
(not quick search) and typing calibre. When it shows tick the box to install
it and Hit apply. One nice thing about Synaptic is that you cna tick as many
boxes as you like before you hit apply and then do something else while it
does its downloading and installing.

Once the packages are updated then you can use any package manager, even the
afore mentioned Software Centre.

BTW, another term to watch is upgrade. Update means to update the list of
applications for the most recent versions and upgrade means to actually
install the upgraded versions. they can be confusing until you get used to
it.