The essence of this book is a constant focus on the bottom line of the business supplemented by a large slice of luck. Firstly Ryanair managed to negotiate the lowest airport fees in Europe by buying up capacity at Stansted when the new airports partnering agreements with other airlines fell through. Strategically this set them up for the long term. Since then rigourous monitoring of costs such as only using black & white printers in their corporate headquarters through to only buying second hand aircraft (in the beginning at least) and using the same model of aircraft on all routes equals large savings in maintenance and overhead costs.
Furthermore most non-value added costs such as pension costs, uniform and training costs are passed to the employee rather than being paid by the employer. This is taking to the max the concept of the employee as just another factor of production and by removing the requirements for experience and career development from all roles O'Leary does not care about staff retention, not even as regards to pilots.
All in all there is a lot that any organisation can learn from the management of Ryanair in terms of controlling costs. If, however, you value your staff and need to retain them, and want to attract customers for reasons other than hilariously cheap prices, ignore this book.