Glen Murray, who as far as I know is a US gentlemen who lives and has lived for a long time in Spain, has written some very specialised handbooks, such as Las Acuñaciones de Moneda en Segovia (30BC to 1869), published in 2009; Casa de Moneda de Madrid (1614 - 188), published 2014; and finally Cecas de Potosi y Lima (published 2016).
These works are fantastic- they have so much detail ( mintage by face value and year), gold or silver content of coins, background information, names etc of assayers and mint masters, superb life size photos of coins, high quality paper, etc - and they are all surprisingly cheap - the Potosi - Lima book, 290 odd pages of fantastic information cost me only 18 euros, and I seem to recall that the Segovia handbook was 15€!
All are published under the imprint of the Asociacion Amigos de la Casa de la Moneda de Segovia: www.SegoviaMint.org and info@segoviamint.org - and they are essential for any collector of Spanish coins.