Five so far. The sixth one is due out on March 16th.
Four books have already been published. Two more are on the way, and will get Published sometime in 2011. And after that, there are at least THREE more books in the series. :):):) You can read more about it on Wikipedia!
There are 4 in the original series: 1) The Awakening 2) The Struggle 3) The Fury 4) Dark Reunion 'The Return' trilogy contains: 1) Nightfall 2) Shadow Souls 3) Midnight
Yes, the TV series is based on the books, but it has been altered in many ways.
The Vampire Diaries has been on TV since September 10, 2009.
It appears to be a popular genre at the time, but vampire and vampire/romance novels have actually been around for quite some time.
In the books they do end up together. But so far the show has been a lot different than the books.... So only time will tell
depends on the type of vampire in question
I don't know there is only repeats of Benidorm instead of vampire diaries 
there has been 22 episodes in all three seasons of the vampire diaries. so 22 :Px
In the books no but in the TV show it has been revealed that she's still alive and never cared about him.
No. It has been made into a TV show.
Well, it hasn't been revealed yet. But I think he does.