I attempted to walk from Lands end to John o groats a few years ago (bailed out on the severn way with a broken knee ligament)and this was one of the books I purchased to help me plan my adventure.
Brian Smailes is clearly an accomplished walker and knows what he's talking about. I tend to find that his advice is more for the "hardened" distance walker and when you bear in mind that he used to sleep of an evening in a "bivvy bag" where ever he found himself, you can tell he doesnt have much time for the softer side of things.
I would take the best ideas from this book and also have a look at Andrew McCloys book "The Lands end to John O'groats walk". he plans it out for you in stages and gives a bit more useful information on accomodation and routes.
There are many things to consider if you are planning to undertake this adventure, i would recommend that you fully grasp what you are getting yourself into. I personally found the three weeks that i had on the road to be rewarding, but it is extremely lonely at times and costs far more than you'd think. Reducing the amount of weight that you carry is essential (carrying a tent and lots of equiptment sounds like a good idea at the time, but after 8 hours on your feet you'll feel differently !)and I would suggest that you have as much of a support crew as you can feasibly arrange. If you go alone as I did, it can be mentally very demanding and to be honest, i wish i had done it with at least one other person.
Make sure you set aside plenty of time to do this walk and try and plan proper rest days. I didnt and I paid the price.
A great challenge and one that few people have done which I'm sure will make completing it all the more special for you. Good luck !