The main idea of the book is simple and compelling: *IF* markets are not efficient (or very, very close to it) then any index weighted by market cap systematically overweights overvalued stocks and underweights undervalued stocks. If you further believe that prices track intrinsic value over time, then cap weighted indexes suffer a performance drag over time, as price errors correct.
The proposed solution is to weight index components by a measure that is not linked to market cap. More specifically, the authors propose linking weights to fundemental measures, like sales, or a composite of metrics like sales, profitability, etc.
The book includes numerous examples demonstrating the superior performance of this suggestion by examining backtests in different geographies and different market cap ranges.
The main drawback of the book is that it is a book. In reality, it is a good essay, or article, or blog post, masquerading as a book. Once you grasp the key message you are safe to put the book down, or skip to the charts if you want to study the backtests.