Unless those characters are growing throughout that "first act" novel, and is essentially broken down into its own Three Acts, I can't see too many sticking it through to read.

Think about the Hunger Games for example. Three books, so three acts of an overarching story. However, in the first book, which does set up the characters and world, you can still break it down into the standard acts. Book Two Katniss is then thrust from what became her ordinary world into yet another change by living the life of a Champion. And the third book, much like a third act, seemingly changes tact. It's no longer focussed on just surviving the games, but from taking down the regime that created them.