The best thing you can do if you want to be interesting is to have an interesting lifestyle. Make sure you do something fun which you could talk about every 2 or 3 weeks. Go to parties, travel, etc. You should go clubbing at least twice a week or more if you really want to get into a talkative state.
If you want to become a better orator I guess you could read "How To Win Friends and Influence People by Dale Carnegie", though the book didn't do much for me personally. I'm sure some other people will have good recommendations for that.
If you want to learn to have fun (without meeting people lol) you should watch Fresh Prince of Bel Air, Jim Carrey, Robin Williams, Eddie Murphy, Chris Rock, or whoever you like.
I used to have the same [problem where I could attract but when I talked too much, interest would often plummet.
You probably need to work on your (body) language skills. Don't lean in, keep your voice tone low, talk with pauses(at a volume to cause the other person to lean in), not too much smiling(sign of weakness), keep your eye-contact strong as a laser beam, don't let another person push you from the space you're standing, etc. Keep everything in moderation.
I recommend that you read The Game by Neil Strauss or The Art of Mackin' by Tariq Nasheed.
