The Colleen Broadhurst Adventure Series by Christine B.
When writing, a successful author should come up with something that keeps his/her readers interested, and in many cases that is writing books in a series. A series makes familiar and likable characters a part of the storyline and keeps the reader interested.
Of course, the first step to any good writing would be to create believable characters, and believable characters are written mostly by creating characters from people the author knows from real-life. Every person an author comes in contact with in his/her life might end up in one of their books one day. That is just one of the drawbacks of being a friend or an acquaintance of an author.
I know that everyone I know looks for themselves in my books, and they are likely to find themselves therein if they look hard enough, especially if they have a unique personality.
Back to the series, concept. Once you get a reader hooked on a series, it is much easier to sell your next book in the series to readers who has read other books in the series. The author just has to make sure they keep a list of the readers who have bought and read the first books.
A good thing to keep in mind, however, when writing a series, is that each book in the series should be a good book as a stand-alone, just in case the reader starts to read it without having read the previous books first. So, the author should always refer to the previous books in the current book, so that the reader is inticed to read the previous books as well.
If it worked for Agatha Christie with Miss Marple and Hurecle Poirot, it can certainly work for you.