Two observations: One, this book requires a long-term relationship. Two, people in the 1800s had way too much time on their hands. This is easily the longest book I've ever read. Richardson is lengthy in his own right, but he also includes extensive excerpts from Campbell himself (who was not known for his brevity). I ended up skimming many of the excerpts looking for the main points and I completely skipped the footnotes, which were also extensive.
All that aside, I'm glad I finally read it. I say "finally" because it was assigned in grad school and it sat unread on my shelves for 20+ years since. Like it or not, I am a product of Alexander Campbell's influence. I grew up in the Churches of Christ, graduated from two universities associated with the the Churches of Christ, and now preach for a church tied to the same movement. I no longer agree with all tenants of the modern expressions of Churches of Christ, but I have deep appreciation for Campbell's efforts and purpose in seeking to restore the simplicity of New Testament Christianity.
I was particularly compelled by his desire for unity. This is still a core value of my belief system and the church I serve. I also appreciated his desire to appeal to the Bible alone and discard all forms of human creeds and traditions (seeing them as the cause of so much religious division today). Of course, ultimately Campbell's "unity movement" ended up splintering itself and there are not three major branches of the Restoration Movement. Yet still, the simple call for non-denominational remains and the appeal to Jesus alone as the sole head and central focus of the church still inspires me today.
I'm grateful for Campbell's influence and find him an interesting character in religious history. However, if you're interested in learning more about him, I would recommend picking up a shorter read. Gary Holloway and Douglas Foster have a great book titled "Renewing God's People: A Concise History of the Churches of Christ." Note the word "concise."