So you did not get my eBooks from Amazon store for free last Sunday? Pity, that you missed it... still you can borrow them (also for free) from Amazon, if you subscribed to their Prime program.
English version here: http://www.amazon.com/Levels-Curves-GIMP-ebook/dp/B00D2M6G7Y
Spanish version here: http://www.amazon.com/Niveles-Curvas-GIMP-Spanish-ebook/dp/B00CLBZ3WQ
If this is the case, upon checking my books you will see a link to their Lending Library... try it!