Alan, there is no substitute for 'Hands on'. I suppose publications are fine. Not having read any, I would imagine they are in a different world from you and I, and would probably be a little intimidating, making you think "I'll never be as good as that." You might even try and copy from a book.....Fatal! You will develop your own style in your own time.
You really need to get down and dirty from the outset.
Have some fun and have a play. Start with a small base and do something simple:-
A road with a grass bank and ditch. A simple flat bridge. A wall. Just make a start, post your progress, ask a question on here and folks will guide and help you.
Even after reading about dioramas, you will still have to make a start with the real thing. To my mind the best way is to get stuck in straight away. You will be surprised how quickly you will gain experience and start to improve your skills.
Don't be afraid to ask. This place is stuffed full of talented modellers who will help all they can. Also, have a scan on here for the various tutorials and diorama builds.
Ron