Preferably something not just focused on one church, one musical style or one approach to worship leading. And preferably something with a bit of bible, theology, and thought to it. I have many thoughts and ideas from what I've learnt down the years, but a good book bringing a lot of stuff together would be good for me and probably more generally useful in our church.
Anything by Robert Webber. I read his last two books, including "The Divine Embrace". He has a horizon-to-horizon vision for worship, and offers as wealth of thought that rattles your preconceptions. He grew up in a stiff, stilted worship environment, but devoted his life to trying to find what makes for real life and godliness in worship, taking cues from both the upcoming generations, the ancient historical church, but mostly from the Word of God.
John Stott's "Life in Christ." Get the hardbound one with the cover of Peter washing Jesus' feet, and lots of great works of art in splendid reproductions throughout. (As Alice said, "of what use is a book without pictures?"
The works of C.S. Lewis, including, and maybe especially, his Narnia series and space trilogy. They are cram-packed with sound theology of worship, and can restore the senses to the beauty, wonder, fun, joy, peacefulness and liberty of worship. Whenever I read Lewis I want to sing.
The books I've read that are specifically about the music aspect of worship tend to be soapboxes for the personal slants of their authors. Some authors who write brilliantly on other subjects get pontifical and dumb when they approach music -- it's so subjective (or, not really knowing what to say, they just get boring). (this said with all due respect to my colleagues who have posted books titles I have never read, and which I probably ought to!)
But in general, I prefer sources that don't "put everything together", but leave the open ends of the trail for us to travel, and thus find for ourselves, among the real people we meet, the true joy and strength found in worshiping God in community.
Absolutely, I have personal preferences about worship music, but I am in a very diverse church where there is little chance that we will ever be able to do music that is to everyone's taste. What is more important is the substance, not the style and a good book on the substance would help.
I have about half of C.S. Lewis output in my bookcase anyway and agree they are very helpful.
I'll look up Robert Webber. Haven't heard of him before.
I agree with the point about books written by musicians, the last time I went into a Christian bookshop the only books I could find were of this sort with a very obvious slant towards one style and one denominational theology. I, for example, like Matt Redman, but I'd prefer to steer clear when it comes to general books about worship as a broader view would probably be more helpful - especially to church members who don't like Matt Redman's style!
Try "Heart of the Artist" by Rory Noland, I have been using it for a small lesson before practice each week. Deals with a lot of issues that worship leaders and worship teams go through, everything from our unique personality to how to deal with confrontation on a worship team. It has changed how we communicate and function, it was suggested to me by another worship leader at a men's conference. Best thing to happen in the worship ministry at our church in ten years. Plent of scripture, not alot on theology.
I had almost forgotten about 'The Heart of the Artist'... I'll have to dig that one up, I've been looking for something to include the team in a 'devotion' before rehearsal to make sure that we are all on the same page with what we are doing on Sunday Mornings.
For a book that is a great read, I like 'Let it Rise' by Holland Davis. It has a lot of good stuff for the team aspect and finding your 'vibe', it also includes some parts that are focused on the pastors part in the whole picture. I have it on my Kindle and go over it every now-and-again.