Below is a list of books for a wide range of courses including courses using counselling skills on the telephone.
If you are just thinking about becoming a student, a worthwhile read would be Experiences of Person-Centred Counselling Training by Laura Buchanan and Rick Hughes.
If it has been some years since you studied, or you need a bit of guidance with study skills, have a look at Step in to Study Counselling: A students' guide to learning counselling and tackling course assignments.
First Steps in Counselling is a standard text in universities, colleges and training institutes all over the UK. It covers all relevant areas of training at this level - theory, personal development and building helping skills. It is full of down-to-earth examples, quotations and activities making it a very stimulating and accessible text.