Secondary sources are handy references for non-controversial facts such as dates, times, names and places. They also necessarily contain the author's bias(es), which can be advantageous or not: if the author is making an argument and states it up front, secondary sources can be extremely useful for examination of history through the perspective of a particular point of view; if there author states no argument, then the reader must simply be aware that every author has a unique point of view, and chances are that the book's substance will reflect it to some degree.
The great advantage of secondary source materials is that to greater or lesser degrees, the author has already done the research for the reader, and the information he or she has found is collated in a more readable, often narrative, format. This makes understanding the history of the 100th Infantry Division easier. BUT! Researchers should remain alert to the fact that some authors perform research better than others, and that the best way to ascertain absolute truth is by examining a mixture of secondary and primary sources!
Books About the 100th Infantry Division
Books About the Campaigns in Which the 100th Infantry Division Participated