I've always wanted to start a forum...

Running a forum just in terms of mechanics is tricky.

Creating a community and building traffic, is harder still.

In terms of expanding your writing? Meh. Probably not worth the time.

But a blog with comments can be interesting, and can actually allow you to give back to the community.

I actually just got off the phone with my attorney, and he encouraged pursuit of a forum. However, yes, he said that blogs is where the real money is (so to speak), and that the best return is there. Forums are tricky, and require a lot of thought as to how to approach it to make it worth one's time, that is true, most definitely.

You must read these posts by Fred Hicks before you ever build a community.
The biggest thing to remember is that word of mouth is the hugest thing you could do to promote yourself. If all your customers are on your forum talking about your book together how will people on other forums find out?

The better option early on is a blog where you treat each of your posts as forum thread by ending it in a question. This gives your fans a sense that you have a central "community" but at the same time still encourages them to chat you up other places.

If you decide to go the blog way wordpress is awesome. If you end up trying to go forum route use SimpleMachineForum. Which ever your choice if you end up using Dream Host (recommended I use them) you can use this promo code to get your domain name free SETHSFREEDOMAIN .

Hope you are able to figure out what the best path will be for your situation.

I am not sure the time put into establishing a forum, promoting it, moderating and maintaining it, and doing your part to keep it active and current would pay off with respect to expanding your writing.

As others have said, a blog is probably a better route.

Hmm, ending blogs with a question. That's a cool idea. I'm glad this thread was started; ya never know what you may learn. Thanks.