The Problem
There are so many different opinions on Plato's Atlantis, there are so many webpages, so many books and so many articles published in scientific magazines, many of them written in languages most people cannot speak and read. It is almost impossible to get an overview and to decide, what is reasonable and important, and what is wrong and superfluous. Therefore people often ask for introductory literature to Plato's Atlantis. But there are no general introductions. Many books provide an introductory chapter, but it is often biased since related to the author's ideas on Atlantis. So reading one book will surely not be enough for a proper introduction.
The Solution
Fortunately, there is no need for desperation. As a pragmatic remedy for the problem reading two books will help: One book of a leading Atlantis skeptic, and one book of a leading Atlantis searcher. Both together will serve as a good starting point to dive into the literature on Plato's Atlantis.
German Readers
For German-speaking readers the following books can be recommended:
General remark
You will find some of these books out of print. If you want to buy them, you will find them in second hand bookshops like abebooks.com or zvab.com. Feel free to trust or to doubt resp. to follow or not to follow these recommendations. Especially do not stop to continue reading on Atlantis after you got a first overview.