Newly-available for the Amazon Kindle in the UK is the respected Cthulhu Mythos Encyclopedia. Amazon notes it as “3rd Revised edition edition (1st July 2018)”. Looks like a £10 digital version of the 3rd Revised edition paperback of September 2008, though I’m uncertain if it’s a digital facsimile or a new layout. It covers the entire mythos, the original work from Lovecraft and also the voluminous lore produced by those who followed.
I’ve always balked at wrangling a slab that big through the postal service, as I have a stupidly tiny modern letter-box and can’t change it. But now I have a 10″ Amazon HD Fire tablet (some software royalties finally paid out) the book is looking enticing. And it would be keyword-searchable, albeit only via Amazon.