Catherine Levison presents a synopsis of Charlotte Mason's methodology in a very user-friendly format. Mason's own writings are voluminous, requiring too much time and effort for the average homeschooler to read through all of them to get to the key information. Levison does a terrific job of honing the information down to the most important components and presenting them in a practical fashion.
A Charlotte Mason Education focuses on Mason's methodology by subject areas such as literature, spelling, science, and art appreciation. It also includes chapters on other critical components: narration as a teaching/learning technique, handicrafts, citizenship and morals, and the formation of habits.
A sequel of sorts, More Charlotte Mason Education offers broader advice about scheduling, selecting materials, and teaching methods. It explains how to create a "century book" at length, a topic that was addressed only briefly in the first book. It includes lengthy lists of recommended books. This book is also a must-have if you are teaching older teens since here you will find one of the few discussions of applying Mason's methods to high school.
In both books, Levison frequently quotes directly from Mason's works, explaining and clarifying Mason's ideas while also adding her own suggestions gleaned from her years of experience teaching her own children and helping other parents implement a "Charlotte Mason education."
A third book, A Literary Education, supplements the other two books with lists of resources that Levison recommends for various subject areas. Levison includes the publisher's information, a description, and the appropriate age/grade level for each resource.
The books were published in 2000, so a few of the resource recommendations need updating. Levison's books should be suitable for both secular and religious audiences for the most part. Some of her resource recommendations are Christian, but the presentation is not overtly Christian.
In summary, if you want to get up and running quickly with a Charlotte Mason approach, Levison's books are the best tools for figuring out how to do so.