I do not see how a book citing an other book is commercial competing. Citations in most cases enhances the original book in same way that research papers cite each other, which then is used as a measurement of the value of the original paper. Some citations that criticize the original book could be used in direct competition, but that follows a very distinct fair use exception that critique and reviews enjoys.

Could you provide an example of a book citing an other book which as a result competed with the book it cited that would not fall under critique or review?