pls, has anyone got any good ebook reader for iPad ios5 cos iBooks doesn't seem to work on my iPad running on ios5

Mine works. Maybe try deleting and downloading the app again?

have tried that but it doesn't work. hw do I add friends and use the imessage

Try resetting you iPad to get iBooks working again. Press and hold the power button and the home button together for at least ten seconds, until the Apple logo appears.

More here:

iPhone, iPad, iPod touch: Turning off and on (restarting) and resetting

After resetting your iPad take a look at iBooks and see if it's working properly. If not, try re-syncing with iTunes once or twice, that seems to have resolved the issue for others. If it still doesn't work you should contact Apple. They have first-class customer assistance and should be able to get things sorted out.

Apple - Support - iPad - Contact Support

Apple - Support - Contact Support

Contacting Apple for support and service

As for another eBook reader, Amazon's free Kindle App for the iPad is quite good:

http://itunes.apple.com/us/app/kindle/id302584613?mt=8

Not sure what you mean about "adding friends".

More about iMessage here:

Apple - iOS 5 - See new features included in iOS 5.

Hope that helps!