Well, maybe not. It didn’t happen that way for me. In fact, my first two books did not sell despite the best efforts of my very capable agent. [Full disclosure: a fact that would have probably killed me if I had known it up front. Two plus years of work, stillborn.] The third book sold in two days.
In this blog posting , an agent muses on how many clients sold their first book, how many sold later books, and how many have yet to sell.