OK, so im new to the Night World too, but my friends sister helped me with it:) With the characters its not like only one, because in each book is other main character but sometimes like in eg. Soulmate you can meet the characters from other books.
So the order is:

1. Secret Vampire
2. Daughters Of Darkness
3. Enchantress
4. Dark Angel
5. The Chosen
6. Soulmate
7. Huntress
8. Black Dawn
9. Witchlight
10. Strange Fate ( Not yet released, but i think it will be in 2010)

I wish You good luck, those books are really the best of ALL!!!

It is:
Secret vampire
Daughters of Darkness
Spellbinder
Dark Angel
The chosen
Soulmate
Huntress
Black Dawn
Witchlight
and no they are not the same characters but they relate to each other. For example in secret Vampire it is about James and poppy but a guy Ash comes in and the second book Daughters of darkness it is about Ash and in that one there are these 2 witches that come in and the third book Spellbinder is about them... you get it?!?!

Night World book series list from first to last
1. Secret Vampire
2. Daughters of the Darkness
3. Spellbinder
4. Dark Angel
5. The Chosen
6. Soulmate
7. Huntress
8. Black Dawn
9. Witchlight
10. Strange Fate

I have just recently start reading these book and there great, but each story has different main characters but they still connect and also characters from the begin series may be mention or show up in different book like in Secret Vampire, Ash (who seems as a bad guy)have a big role in that book but in Daughters of the Darkness he falls in love.Ash also show in small parts in Dark Angel ans I heard he will be in Strange Fate.Even though the main characters change the series still flows together like one book.