They're definitely a legitimate agency. Denise has been in the business for many years in Canada and has signed and represented many well-regarded Canadian literary writers. She has a reputation as a hard-nosed negotiator who works hard to get good deals for her clients. I know she's irked some publishers in the past because of this.
I actually queried her about 12 years back when I'd had a fairly big story publication and she talked to me on the phone, which was quite generous of her. She explained that I'd need more than a few stories to sign with an agent, but was open to me once I had a novel ready to go. (I knew nothing about agenting at that point). The novel ended up being a lot further away than I'd imagined, so I never did approach her again, but it had nothing to do with her reputation.
She mainly (perhaps only) represents Canadian literary authors in fiction and nonfiction. One last thing - I've been involved in writing education for some time and I remember one of her clients told me once that Denise had wanted all requests for her time (reading, teaching etc) to go through her, and would have refused anything that was too low paying (which my program was at the time). So she had to make it clear to Denise that she'd be in charge of that part of her career. So definitely a tough cookie who fights for her authors, which is what you'd want in an agent.