It would be ridiculous for readers of Lance Armstrong's books to sue him. One must consider how many book are purchased daily and then consider the fact that not all readers are happy with the content of the book they have just read. We are not always satisfied that the book was a good choice either because we know some of the facts to be false or simply not good content. The same would apply to Armstrong's books.
Most people who write autobiographical works lie in some way. There is always going to be an agenda behind why someone does any kind of non-fictional writing. The people who read his book are simply out the price of the book, that is all. It would be petty for them to sue him.
There is no good reason for the readers of Lance Armstrong's books to sue him. Yes he cheated, but reading his books was a personal choice by these individuals. Lance didn't force anyone to buy or read his books. If anyone took this to court they would not win anything.
A book, especially when written by a distinguished person in a field of sports, is not meant to be a step-by-step instruction booklet. Often, when an athlete writes a book it is meant to be either an autobiographical account of their life, or it is meant to be an inspirational story to motivate people to achieve their dream. Simply because an author is later found out to be a hypocrite does not mean that the people who read his or her books were deceived. The information in the books can still be followed. There is no basis to sue because somebody said one thing and did another.