There is a lot of information about Wesley and the Methodist movement scattered online. You have to watch some of the commentary on Wesley because people on left and right want to read their agendas into Wesley's thought and action.

A good place to start is with Richard P. Heitzenrater's Wesley and the People Called Methodist. This is a history of the Wesleyan movement.

Wesley was greatly influenced by the German Moravians and also Luther's writings. It was in a Moravian Bible study where, as they read the preface to Luther's commentary on Romans, that Wesley "felt his heart strangely warmed."

Good luck with your book. I am thinking seriously of writing a book along the lines of re-imagining the church. I am burned out with churchianity as it is practiced today. I have not been to church but once since I retired from the ministry three months ago and I could not wait to get out of there the Sunday I went. That is a shame.

The Lord be with you ...