I've read numerous books and have studied his biography intensively throughout my adult life. It is part of my desire to understand the story of my native heritage. He is the unifier, the conquerer. Hawaii's first warrior chief to have conquered all the Hawaiian islands to forge a kingdom to enter a new age of Global travel, trade and colonialism.
His life story is amazing, inspiring, and comparable to any mythical, legendary figure of any Western historical account. He was referred to as the Napolean of the Pacific.
If you're interested in reading a fairly accurate summary, Wikipedia has a good summation of his life story.
I also just bought a new, hardcover children's book, entitled Kohala Kuamo'o: Nae'ole's Race to Save a King. It regales the story of his birth, which in some ways parallels the events surrounding the story of Jesus Christ's birth. Legend tells that he was born while Halleys comet was in the sky, which portended the birth of the Chief who would eventually conquer all other Chiefs.
So the ruling chief of that time, ordered him killed. But he was taken into hiding and survived the attempt to kill him. I love this book, for it is written in both English and Hawaiian. Hawaiian language neared extinction in the last century, but it has undergone a revival in the last several decades. Children's stories in Hawaiian are good way to continue the resurgence of the language.
Finally, I would recommend an excellent book that I have read 3 times already, and will probably read it a fourth sometime in the future. It's essentially a compilation of the translated works of a serialization of Kamehameha's life story that appeared for a period of time in the Hawaiian language newspaper in the 18th century. It is told through the story of his lua instructor (Hawaiian traditional martial art), Kekuhaupi'o.