For your information I have now got hold of a copy of the Lee Jackson's and Merlin Blencowe's books.
The Lee Jackson book is pretty useless to be honest. In fact it's hard to say anything positive about it.
In contrast the Merlin Blencowe's is top notch. Probably the best book on guitar pre-amps I've seen, with a load of info not found anywhere else. I would warn any prospective buyers that it is not for beginners, and has plenty of equations in it. Nevertheless, even if you aren't into the maths then you will find some very useful circuits/ ideas in here.