What is this book about, and who are the characters we meet in this book?
The Little Foxes is a play and not a book. Students often refer to plays as books, which (since they are reading the text in a bound manuscript) is OK I guess, but it also leads to the confusion you seem to be under, which isn't OK. You had listed "novel" as one of your tags (which I edited out). This text, distinctly, is not a novel. It is a play, which is as different from a novel as a novel is from a poem. They are completely different types of texts -- apples and oranges, to use a worn out analogy. This is just the sort of misapprehension to which calling scripts "books" often leads.
All that being said, if you are in need of the basic information -- plot and characters -- about The Little Foxes, you can go right to the Enotes Study Guide. Below, I have linked the Introductory, Summary and Characters pages.
Here is some general information from the Enotes Introduction, to get you started:
Lillian Hellman's cynical play of family greed and revenge, The Little Foxes, was acclaimed an instant hit after a hugely successful opening night in 1939. . . . [T]he Hubbard siblings steal, deceive, and plot against each other in their efforts to invest in one of the first cotton mills to industrialize the New South, a plan that stands to win them millions of dollars. Regina, temporarily cheated out of her share by her brothers, even "murders" her sick husband by refusing to fetch his medicine when he threatens to obstruct her from taking part in the investment.. . .The Hubbards are a family prone to deceit, caught in a cycle of revenge not unlike Greek classical tragedies.
The main characters are: Regina Giddens and her two brothers Leo and Oscar (plus wife Birdie) Hubbard; and Regina's husband Horace and daughter Alexandra.
For more on the play, please follow the links below.