Promoting at a convention?

How big is the convention? You might have some luck as a local author at a small con without a whole lot of competition in artist alley, though I'm admittedly not the right person to ask about smaller conventions.

At a con people have actually heard of, though, I don't think you'd have much luck. In general, people shopping at conventions want fandom merchandise or unbranded cute things like stuffed animals or jewelry. Original art is a hard sell, and a novel is, essentially, original art you can't size up at a glance. (I always feel bad passing tables selling original novels or comics, honestly, because they're almost always deserted.)

Also, looking at your novel's summary... it's definitely not something I'd want to buy at a con. I'm there to have fun and spend too much money on anime figures. I don't want to think too hard about real-world issues, and I don't think I'm alone in that.

I've been going to conventions (comic cons mostly) for eight years and can hopefully offer some advice you might use. Yes, banners and signage are important. I wouldn't have just one copy of your paperback - I'd have them in stacks if practical. As far as book-related merchandise, you might hold off. Merchandise (branding) is only good if your work is known, in my opinion. Otherwise there is no significance for the purchaser, unless the merchandise itself is useful and priced low enough to attract them. If you have reviews, by all means make signage out of them so folks have an idea that they're buying a good yarn.

Artwork is always a good thing to sell. Also, look at the grid towers other folks are using. You can do more vertically and have a better chance of catching the lazy eye. One word of caution. If your artwork is so-so, it might work against you considering the artists around you, so get a second opinion from someone who's critical eye you can trust.

Finally, understand that folks generally don't come to buy books, so you probably won't make a lot of money. Selling other hand crafted stuff can offset the financial strain when tables are $200 and above.

All of that sounds good, but as someone who has done this sort of things many times over I have to say the biggest draw is you. Don't just sit back behind the table. In fact maybe don't sit at all. I often end up standing next to the table, not even behind it. Actively engage passers by, have an elevator pitch ready for them so you can explain why they'd love your book. I basically hand sell each and every one of my books at cons, even at bookstore signings. It's slow going, one by one, but you can definitely sell out that way. So yeah, talk to people. Call them over, be friendly and really try to sell them on your work (but here's the kicker, you also need to know when to back off, make sure you read people's body language and don't push too hard).

Rather than paper bags that people will toss as soon as they get home, you might want to think about business cards. Now would be a good time to have a basic website to go on the card. Some might not want to buy right there, but will look it up later.

And, not a con-goer, but from experience of craft shows, etc: Read whatever info the committee gave you when you signed up (if not before).
Sometimes they provide a basic table cover, sometimes it's all on you. You want something (a large sheet would probably work) to drape over the front to almost-floor-level, to hide the boxes, etc. that you will store underneath. Also, any personal stuff - CARRY YOUR MONEY SECURELY ON YOUR PERSON. Decorative table coverings, banners etc. can go on top.
Find out what, if any, arrangements have been made for booth coverage if you need to eat, go to the bathroom. The only thing more off-putting than an empty booth is one where people are obviously 'on a lunch break'.
And, I gather you've been to the venue before? What's the lighting like? A big craft show here moved to a new space, lovely high ceilings, but not designed to house rows of walled booths. The light did not reach past the fronts of most of the booths. Some boothholders had their own lights, but many were, literally, left in the dark. Especially important if you have artwork and books.

If you don't have room for stacks of books on the table, have at least two. One, flat on the table, for them to peruse, and one, on a bookholder or some such, up at an angle to catch people's eyes. If you can only do one, do the one on the holder. Flat on the table does not catch the eye as well.
Also, a matter of personal taste - for the 'reader', at least, try to use a copy that you've read a few times - brand-new, absolutely pristine books may put people off from having a quick browse, for fear of 'you broke it, you bought it'. (Of course, you actually sell them a perfect copy.)

And, what Toothpaste said:
Work your booth. Do not huddle in the back, do not play on the computer or the phone, no matter how slow it's been. Do not look like you'd just as soon be left alone. You are not some hired kid, you are the proud booth renter.
On the other hand, don't leap at people and try to drag them to your booth. People flatten their ears to avoid the hard-sell they see coming.
Front of the booth, or just outside, nod and smile to the passersby. (And, yes, most will pass on by, but keep trying.) Have that 'elevator pitch' ready, show off the artwork. A little chit-chat doesn't hurt - "How're you liking the show?" "Been here before?" Mention some interesting feature. All in the interests of luring them closer. (Also the reason for the hard candies.) You don't want the booth to look deserted - customers are sheep-like: if everyone else passes by, they are tempted to do the same.

Good luck!

Don't panic.

Smile, say "Hi!" to people, ask if they'd like to hear about the book. Be honest, be friendly within your comfort level and be real.

It's surprising how many sales you can make by being honest and yourself.

So, has the convention happened yet? And, if so, please let us know how it went. Remember, either good or bad, it's a learning experience for the next one.

I think it's an excellent thing to do. Of course I have to admit, a couple hundred bucks to me is what I spend at two visits to the grocery store so I don't see it as a huge investment.

If your book is good, you won't know it until people read it. A snowball rolling down a hill has to have a good start.

If it's not good enough, write the next one. Look at how much experience you have now. My belief: nothing is a loss if you learn something from it.

A writer friend of mine, (ten books out now and they are doing well), had one of her books at an 'event'. I don't know much about it but I enjoyed her report that the booth next to her did a brisk business in some kind of weird beads that were the current fad.

Like frimble3, I await your report.