Over the years I have read many books about ‘How to Improve your climbing’, some of them have been very helpful, whilst others have been less so. Although there are some new books out like Coaching Climbing that is aimed at coaches helping young climbers train. Many of the activities in there are great for helping anyone’s climbing. However one of the best book I have read on the subject is a rather old book called performance rock climbing is a great all round book on training and skill acquisition. There are a couple of good book by eric horst on conditioning for climbers and training for climbers.
If however you want to learn about rope work techniques then consider getting hold of Libby Peter’s Rock climbing: Essential Skills and Techniques.
Alternatively if you were to get Climber Magazine this month you’d get an excellent training edition, with multiple articles by Training Guru Neil Gresham, as well as some other writers specialising in nutrition and sports injuries.