the only book by David Crystal which I have read is one I bought many years ago (1986!!), called "Listen To Your Child - A Parent's Guide to Children's Language".
It is utterly brilliant, and explains very clearly how babies, toddlers and older children acquire, develop and refine their use of language. It is very well worth a read, and I referred to it often, being fascinated with the different ways my children use language.
On a sidenote:
DD2 - an accomplished exponent of the art of text messaging, though her texts to *me* are always grammatically correct and punctuated, LOL - was complaining bitterly that her sister, DD3, was abbreviating text messages so much that DD2 was finding it difficult to comprehend :-)
How language develops and changes is a mysterious and wonderful thing. I am still - and suspect that I always will be - a stickler for clear and appropriate punctuation and grammar, but I can still appreciate the humour and ingenuity of our amazing adaptive language skills as humans.
I will certainly check out our Library's books by David Crystal, Ian, and thank you for inspiring me to do so. I love having book recommendations :-)