The best information about Geert Hofstede can be found on his own website: http://www.geerthofstede.nl/
There you can find details of the two essential books that detail Hofstede's research: Culture's Consequences
and Culture and Organizations: Software of the Mind
. Since I finished teaching my own course on comparative culture (using the Japanese translation of the second book), another edition of the second book has appeared, a revised third edition. Amazon helpfully lists a number of critical reviews of this book, mainly from academics like myself who have used it in their university classes, and, as someone versed in statistics, you will be in a good position to see the liberties that Hofstede takes with his data.
Gladwell accepts Hofstede's 'dimensions' without any question and uses these in his chapter on the 'ethnic theory of plane crashes'. (Gladwell, Outliers
, pp. 202-209).