It's interesting to see that Jastram's Golden Constant, which has been recently updated in a new edition is out of stock on both Amazon.co.uk and Amazon.com.
I am still reading mine along with several other books. It's a unique kind of work and is definitely worth reading to get a grasp of the true power of gold and you can pre-order from the links above.
In the meantime, lots of bullion merchants have had their stocks replenished and I took the opportunity to place an order for various gold coins while the premium are very low and availability is high. Silver is still quite expensive, with premiums of about 20-30% before VAT or GST depending on the country.
Interestingly, please not that gold is not subject to VAT nor capital gains tax in the UK. So it's really the best invesment you could possibly make in the UK. Unfortunately, silver is subject to both.