A Publishers Marketplace search turns up no sales in the past twelve months for either Susan Mears or Owen Burham (not all agents report their sales, keep in mind). The last reported sale for the agency is December 2007.
The only mention I did find was on the page of a literary scout called Freda M. Chaney. Ms. Chaney has
a webpage, which gives a page to
the Susan Mears Literary Agency. That page takes its copy from the Home page of the
Susan Mears agency's website:
"...The Susan Mears Literary Agency is widely regarded as being the best agency for Mind, Body and Spirit titles. We are actively expanding our list to include projects in the field of Fiction as well. Titles must have an inherent spiritual message and be broadly compatible with the company's aims and ethics.
The Mears site has a list of their authors (but no links to websites for them). The home page mentions a couple of them specifically; the first--referred to as "One of our best selling, authors,"--is Peter Lemesurier, an academic seemingly prominent in New Age circles, whose book on Nostradamus was released last year through what appears to be a small indie press called New Page Books. Their
submission guidelines are...interesting, but they look legit enough.
I Googled about ten names from the client list; most seem to be with small indie presses; at least one is self-published. But I don't know much at all about that particular market (the New Age-mind-body-spirit type market); I know the names of a few publishers (Llewellyn, obviously, and a few smaller more specialist ones like Capall Bann [my personal favorite]), but I think those books in general do tend to be more small press, so I'm certainly not comfortable saying the agency isn't effective based on that. Certainly the search results for the names I Googled seemed to turn up lots of results, and I got the impression these people were/are well-respected in those circles (again, that's just my impression, I don't know enough to say whether or not that's a true inference).
I will say, though, that most of the pub dates for the authors I Googled were older; I found only one publication in the last four years. Their
Current Titles page on the website appears to show the same thing;
some of those current titles are ten years old at this point (and some are
perhaps out of print now?).
In fact, a large number of their "Current Titles" do not exist on Amazon at all, now that I've done more searching. I think it's fair to say almost none of them do. But...some of them have similar titles listed on Amazon. For example, they list TEACHINGS FROM THE CELTIC WHEEL by Andy Baggott. That book doesn't seem to exist on Amazon (UK or US), but
entering that title gives this result: a book called THE CELTIC WHEEL OF LIFE by Andy Baggott. THE CELTIC GODDESS by Claire Hamilton doesn't exist, but there are
a few pages of Celtic Goddess-related titles by Claire Hamilton.
Almost every title they list on that Current Titles page has the same issue; it's either not listed at all, or a different-but-somewhat-similar title is listed, and all of those "similar" titles are, again, years old. (There are some clickable book covers at the bottom of the page, but clicking them only brings one back to the top of the list; they don't link to any outside websites.)
It's possible those are upcoming titles, perhaps?
I don't know, but I find it...odd, frankly.
Charging $50 to "assess," though...that's a problem. It's especially a problem if--
if--we're talking about an agent whose sales are dwindling. Again, I know very little about this particular market, but I'm not seeing anything that would justify a fee of any kind even if charging fees wasn't flat-out unethical. Which it is.
Hope that helps!