No.
Never.
Reputable agencies are overwhelmed with submissions already, the last thing they need is to put in ads asking for more.
These ads are placed by people who will ask you to send them something, then will gush over how great a writer you are, and then start the process of extracting money from you.
First it might a small reading fee, then they’ll discover that your book needs editorial attention before it goes to publishers and they’ll be happy to help you for a fee or will happen to know someone who can do it for you for a fee.
Eventually (when you stop being willing to send more money) they’ll either say, sorry, we tried but nobody wanted it, or they’ll “find” a publisher who loves your book and wants to publish it…but first you’ll have to pay for further editorial consultations, or the “publisher” will ask you to co-finance the publication of the book (the split will be 0% them, 100% you).
There’s nothing wrong with companies who publish your book at your expense—there are reputable ones but they will be very open from the start about the cost and what you are actually getting. In today’s difficult climate, self-publishing or using a print on demand provider can make a lot of sense for certain kinds of books but, again, the aboveboard companies are very open about the terms and what you get and don't get.
Unfortunately there are others out there posing as agents or publishers who are not far removed from the Nigerian “send me your bank account details and I’ll send you twelve million dollars and you can keep ten percent” hucksters.
Don’t fall for them.
(Want more help writing and marketing your book? Check out "Your Writing Coach," published by Nicholas Brealey and available from Amazon and Barnes & Noble and other online and offline retailers internationally.)
