Not only books. I recommend Mel Duke's blog. Mel was my "spiritual father" way back in the 1960s, durng the year I was stationed at Lowry Air Force Base, in Denver, Colorado. We met at the Christian Servicemen's Center, and I spent many, many hours with Mel and his wife Mary Lou. They are now living in Estonia.
William Wilberforce wrote a book, which I recommended a few weeks ago: A Practical View of Christianity. I just finished reading an abridged version Real Christianity which I also recommend. It was originally published in 1797, with the full title A Practical View of the Prevailing Religious System of Professed Christians, in the Higher and Middle Classes in this Country, Contrasted with Real ChristianityIt is now 210 years old, but it is equally relevant in our day. I hope that the 200th anniversary of the abolition of slavery will help rekindle interest in Wilberforce, his life, his faith, and his book.