If I were to recommend one book on Prayer for anyone remotely interested in discovering what on earth it is all about it would be this one!
A couple of highlights...
"God wants you to be the fullness of what you could be. You cannot become this if you do not allow Him to enter into you. You do your feeble search for Him, and He will do His mighty search for you. 'seek and ye shall find' The 'you' God seeks may not be the 'you' of whom you are aware. it is the essential you, the real you, the fullness of your potential. The transformation from one to the other, the realising of that potential you, may take a lifetime. Few of us will ever wholly achieve this complete surrender. But all God needs is your desire." pp 22
"Prayer is essential an attitude. We trust God, we believe in Him, we turn to Him. An attitude is something permanent. So how could prayer stop when we , as it were , stop praying? It would be as if your relationship with your parents only existed when you were in actual contact with them" pp 29