I am not a self-published author, at least not yet, but as part of my research, I've been reading self-published ebooks on Amazon. As a writer, it's an excellent exercise in what not to do, but as a reader it can be an experience that leaves one's eyes spinning round as one slaps one's head against the e-reader in sheer frustrated fury.
First, lets talk about the difference between a serial and a series, because too many self-pub authors seem to have no clue (either that, or they're outright lying, and I prefer to believe them ignorant than deceitful).
A serial is single story published in parts. A popular form in the 19th century, serializing has become popular for self-pub ebook authors. For one, a complete novel might sell for $4.99 but a novel published in several parts, even with the first offered for free to "hook" the reader into buying the rest, could sell all together for nearly twice that.
A series is two or more books about the same characters and/or setting. It may or may not have an overarching plot. The alphabet detective books by Sue Grafton are an example of series without an overarching plot. The Harry Potter books by J.K. Rowling are an example of a series with an overarching plot. What each book in both types of series has is a beginning, a middle, and an end. Book one of the second type doesn't resolve the overarching plot but it does solve the immediate story problem. The point is, there's an end, a resolution.
The worst thing is to buy Book One of a Series and realize it isn't, it's merely Part One of a Serialized Novel. It makes me as a reader feel lied to, and I won't buy the rest no matter how good it may have been. I'm not opposed to serials, but for the love of all things written, correctly label your work! Your readers will thank you!