The English Bridge Union has a pair of teaching manuals entitled "Beginning Bridge, Book One" and "Continuing Bridge, Book Two". It also has a file entitled "Standard English Acol, Foundation Level System File 2017" and you will find it on the internet. You might try the EBU for help and will be pleased with the result. There is also the "Really Easy" series that you might find useful, too There are not that many books on the subject and the ones that are, are probably dated. Ron Klinger has two entitled "Basic Bridge" and "Guide to Better Acol Bridge". My personal preference is "All About Acol" by Ben Cohen and Rhoda Lederer. It was written at the time when the variable notrump was popular and it suffers from the problem that while the variable element is still alive in some quarters it is possibly out of fashion in a world where 1NT 12-14 hcp openings are the norm. Nevertheless I have found that the principles expounded in it are alive and well still. It needs to be read carefully as so much stuff will slip by if you are not paying attention. A considerable advantage is that to-day when we open at the one-level in any of the four suits four cards are a guaranteed minimum holding. Mind you, some of the bids are tricky. With "Precision Bidding in Acol" you need to be on song with your partner, not everyone likes the style or understands it. "Acol in Competition" on the other hand, is an idea source of information for any partnership. If you need further information "Acol Index" by the same Crowhurst is a useful guide when wondering what particular bids mean or should mean. It is true that there is much need for an up-to-date version of AAA but where to start is possibly the problem. There doesn't seem to be a standard system