210-260 OCG is the primary, i also purchased this book for the firepower piece because of my job and the exam:

https://www.amazon.com/gp/aw/d/B0784D4ZQY/ref=pd_aw_sim_351_3?ie=UTF8&psc=1&refRID=AQYFGY3ZDT26A3W37AZY&dpPl=1&dpID=71pGCcBogvL