The past weekend I have been reading Sakakibara Kunihiko's Okehazama Kassen Kenkyu. This book is informative and useful. However, it is extremely difficult to read like most academic books. If you are looking to see what went into Nobunaga's or Imagawa Yoshimoto's head during the battle, this book does not do it. A historical novel will do. That being said, this book goes into a lot of the local geography and landmarks.